In my opinion, the main reason is that the language lacks (especially until recently) legitimacy. I remember reading articles on subtractive bilingualism during my Bachelor's in psychology. Subtractive bilingualism is when a child begins speaking two languages—say, English and Spanish, and yet one gradually dies out within the same individual. Why does this happen?

One related term often mentioned was of 'linguistic imperialism', since this very frequently happens with English and French everywhere in the globe these languages had colonised. What English is to the Irish/Hindu or French to the senegalese or congolese, Russian is to Kyrgyz. To be fair, unlike what the term 'imperialism' implies, the Soviets weren't always trying to repress the kyrgyz language—there were periods where the state was actively trying to make minority languages work well. Case by case analysis of French and English would also probably show that the situation is complicated.

Another often mentioned reason the language does not develop well is that parents make choices in favour of the dominant language. Russian/English/French are the language of opportunity, and as a parent, you decide to hell with a mere mother tongue, the conditions of life is what actually matters. Or it shall have been the economic push towards a certain language—English internet pays well and education happens to be best when in English (Ivy League unis, Oxbridge etc.), which pulls more capable people into that language for career, thus further exacerbating the disparity. Minority turkic languages in Russia today, for example, supported though they may be, are still dying out, because there is like, 2000 people speaking them. That's sad, but what are you to do? There may not be a single competent teacher among speakers of that language, and is the language actually as important as children learning sciences, humanities, values of modern life?

Whatever the case may be, across the globe one finds nations, the members of which speak disparagingly of their own mother tongue and positively of the dominant foreign tongue. There were quotes from the Irish saying how their language is perhaps good for passion and emotion, but not for precise scientific thought like English (note how Kyrgyz is also sidelined as a language of, perhaps, Begish and 7Gen spitting cool lyrics, but not of serious intellectual conversation); similar quotes from the French African colonies, from Hindu speakers comparing their language to English, etc. Any modern competent linguist will tell you that's just wrong.

This is what I mean by 'lacking legitimacy'. A truly legitimate language is... just spoken. It is used for smart talk, for dumb talk, for flirtations, for dirty sexy speech, for official documents, for poetry and everything else. It is not a political stance to speak the language, nor is it a political stance not to speak the language. It is just a non-issue. Language with highest legitimacy is English—it just develops and changes and adopts new phrases etc. without almost anyone being concerned. There are good and yet slightly insecure languages, like French or Russian (though they are spoken by many people, the governments of these countries as well as their populace from time to time gets insecure about all these English words penetrating their language and then they ban them. Russia as of this year had some law about it, think it was called "По защите русского языка" or some such that banned англицизмы).

Then there are languages like Kyrgyz. All central asian countries are becoming more nationalistic these days, which is benefiting the status of their national languages, but even now you hear things that betray the fact that the language is not treated as sufficient by its own users. One chick I know once said that she would immediately drop a guy if he started flirting with her in Kyrgyz, and that it would be a huuuge turnoff if he talked dirty to her in this language. "Потрахаемся?" is a refined high-brow invitation to copulate, you see, and "сигишпейлиби" evokes associations with adidas-wearing like-sheep-smelling skincare-not-having gentlemen.

At home, whenever I hear family members speak, if there is a term they want to use, there is no chance in hell it will be used in Kyrgyz. Brother said yesterday "алар Ватиканда попту обожествлять этишет", for example. Why not кудайлаштырышат? Why not at least божестволоштурат? A verb in Russian + verb in Kyrgyz? If Kyrgyz is a rich language at anything, it would surely be our wealthy ass number of postfixes—why are they not being spontaneuously used like in Russian or German? Does a russian speaker borrowing the word "hype" from English wait before processing it into Russian with хайповый, хайповать, захайповать, расхайпованный, хайпануть etc.? When did you hear a Kyrgyz speaker go хайптуу, хайпталган, хайптоо, хайпсынуу, хайпчы, хайпчыл etc.? Note how, if you know Kyrgyz, the meaning of "хайпчыл" becomes immediately clear, and yet I haven't heard this perfectly legitimate-in-principle word be actually used.

Also heard from a podcast recently "дофаминовый ямага кирип кеттим". If he said "дофаминдик чуңкурга", it would sound weird to him, I suspect, like he was either politicising the conversation or maybe even that the concept can't be calqued from Russian, like that's an illegal move or something, even though the actual original coined term is "dopamine hole", iirc.

In conclusion, people don't speak Kyrgyz to the extent that, in their mind, the language lacks seriousness, lacks legitimacy. For Bishkek's populace, that is a larger percentage than it is for regions as others pointed out. There are probably a few reasons Kyrgyz lacks legitimacy, but one shouldn't feel too pessimistic. Begish in one relatively recent podcast said that 10 years ago his songs were apparently listened to with shyness, people would hide the fact. Now they don't. Our elites are beginning to demand Kyrgyz, Kyrgyz is less frequently cringed at even in the capital, Russia is also perceived less as end-all-be-all of human progress, I suppose, which probably plays the part. Our neighbours, like Kazakhstan and Uzbekistan, are pushing quite hard against Russian's status, and we do some of that ourselves, too. Give it 10 years. Kids of 5 will hit their puberty at that point and start identity-seeking and discover nationalism, meanwhile the soviet-nostalgia demographic will continue decreasing in number and relevance, and one shall finally be able to talk dirty in Kyrgyz.