I see more sweaty tryhard groups than chill casual ones personally. The chill ones are far and few between, from my own personal experience. There are a lot of people with a certain dedication and ambition when it comes to raiding.
Aside from that, maybe its also that this kind of raid encounters are just not everyones cup of tea? Because see here:
No it does not. Most content is "singular room with boss". (read - most, not all. I know there are exceptions, but the next non room with boss instanced content is over half a year away for when field operations drops.)in fact the game offers a lot of diversity.
Trials? Singular room with boss.
Storymode/Savage Raid? Singular room with boss.
Chaotic? Singular room with boss, again.
Dungeons and 24 mans do at least change it up with some trash in between, but mostly, FF14 is bosses.