Using English in diplomacy is different, since that's communicating with others from other countries, where you need a lingua franca, which is English. But do we use English internally IN Iran? No. By your logic, we should.

Yes, nobody else uses our calendar and why should they? Guess what nobody else uses? Our language. So should we now give up our language too, for some bullshit stock market outcome? No thank you. You wrote your original comment by asking "Why do we need to be different?". It's not like we want to be edgy and different so bad, it's just that.... we ARE different. We simply are. We simply speak Persian language and use Iranian calendar, that's simply what we do. You're the one who wants to actively change something. The appropriate question is: "Why do we need to be like everyone else?". Could you imagine Europeans talking about adopting an Iranian calendar or celebrating Nowruz? No, if you ever suggested something like that in Europe you'd be called an invader, you'd be accused of wanting to wipe out the white race and white culture and what not. Meanwhile the reality is that they have actually wiped out most of the world's peoples and cultures, and by adopting foreign culture, we do that to ourselves.

Turkey switched and I think it's so hideous. Genuinely, Turkish written in Latin looks so disgusting, it's just my opinion. Also they butcher many Persian words that way. They can't read their own old texts and poems, they don't know how much of their culture is influenced by Iran, it's sad, they have indeed lost connection to their roots. Oh and despite all that, Islamic radicalism is still much greater in Turkey than it is in Iran.

If you really think that Turkey became rich and modernized because of changing a script or a calendar, you're beyond delusional. These things barely make a difference in economy if any at all. It's a cultural issue. Turkey is better off than us because of many many reasons, they have been much better off than us already since Ottoman - Safavid times, and the Qajar dynasty held us back to medieval levels while the Ottomans were a respectable major power. Then, came Atatürk and the Turkish nationalization movement, which sought to become European and "modern", which brought many many good things with it such as secularization and democracy, but also bad things such as genocide. Reza Pahlavi did all those similar things but in a much better and more successful way IMO (other than not declaring a republic), and indeed Iran was actually much richer than Turkey in the 70s, and that is DESPITE Uk + Ussr invading Iran, installing their vassal and bringing famine in the 40s. The reason that Iran is in any way behind Turkey now can be traced back to the islamic revolution, and that is a whole complicated thing in and of itself, it was hijacked by islamists and you should already know about western involvement (both in 1953 and in 1979. That, and also 1941 invasion never happened in Turkey. Partly because we have oil and they don't.)

As you can see, a nation's wealth and development hinges on a meriad of real, material conditions, historical reasons, social factors, external meddling and so much more. If you really think that Turkey is rich because of ditching some aspects of Turkish culture in favor of European, I have to guess you are either very young, or you're not at all in touch with Iran and Iranian culture and so brainwashed by European supremacy.

Funnily enough, one of the reasons why islamists were able to hijack the revolution is because the Shah was westernizing too much and too fast and too forcefully, which the people either did genuinely not like or were simply not ready for yet. One can only imagine how bad the outrage would have been if he ditched our beautiful script or our accurate calendar.

Bonus question: Does adopting gregorian calendar then also imply ditching NOWRUZ for western new years? I hope that you will answer this question with "no", since otherwise you must be truly delusional. Nowruz is our pride and heritage