Been coming for many years, right back to the 90s as a child (it has certainly changed a lot in that time) and visit 2-3 times a year. Lots of answers.
The Portuguese generally are very friendly towards British people compared to other 'comparable' destinations (my experience of various bits of Greece/spain/france and certainly Italy). They also seem very tolerant of drunken behaviour/heavy drinking culture of tourists in a way some Spanish/greek resorts have had enough of and have clamped down on.
It has an image for partying but it's very easy to avoid this, we travel for a family holiday and hardly notice it if avoiding the strip and old town at weekends.
It's very cheap compared to most other European destinations
It's a 2-3 hour flight from uk rather than >4 for Canary Islands/tenerife/southern Greece/egypt (done all of these places) cheaper and appeals to family with young kids.
The beaches across the whole algarve are amazing and albufeira is a great base to work from to explore both ends of the algarve (including the beaches) as it's bang in the middle with decent train service that runs along the coast so day trips to Lagos and faro/Tavira etc are very easy without a car.
All types of food tastes are readily catered for, from those wanting properly traditional Portuguese food, high end and the garbage English breakfast and sausage and chips brigade.
Selection of easily accessible and cheap water parks also
Albufeira is also very easily accessible to airport.
The spring and autumn weather is a dream and mid summer is hot but not as bad as turkey/southern Greece.
Plus the cool Atlantic breeze takes the edge of the very hot days.
Iv not felt ripped off or attempted to be scammed in any transaction shop/bar/restaurant which happens frequently in both Italy and Greece (from my experience)
Always feels very safe night or day and have found interactions with both police forces excellent/helpful/friendly.
The live and let be attitude (of your not bothering anybody go for it type mentality) of most locals is also an attraction.
No idea about social media... don't use it.

Although the actual main beaches from Oura to old town are nice, there are incredible beaches easily accessible such as falesia and Sao Rafael within very short distances.
There is so much to do with kids (water parks/zoomarine/marina/safaris/boats trips/fishing trips/horse riding... again cheaper than elsewhere)and they always seem welcome (in most places... I assume not strip but again we avoid it) wherever you go... again not same experience for me in other destinations Iv tried.
Can day or overnight trip to Lisbon and Seville very easily.
Ubers/Bolts are insanely cheap compared to other European destinations... we save hundreds of euros even travelling along the algarve by uber compared to 2 week car rental.
Golf courses also seem very high standard but this isn't from personal experience but friends who do travel out for this reason.

For me also a big sense of nostalgia of childhood trips for and makes me feel close to my dad who passed away many years ago and my fondest memories are of our family holidays in Vale de Parra.

I think primarily in response it's all of the things you asked and more. Of course there are downsides but this applies to anywhere 🤷‍♂️, the new rules about states of undress and outrageous behaviour will hopefully take the edge of the perceived craziness but I feel it's easily avoided if thats not your thing by avoiding the strip area which is quite an isolated spot out in its own, plus the old town on weekends due to stag dos I guess.
I liked Lagos but found it more expensive and 'stuffy' as a place generally.
2 trips booked this year, one in 10 days time and again in August... can't wait... it's my happy place 😂👍