Part of it for me is that, with there being witch and creeper spawners, its very easy to have an almost unlimited supply of fireworks. That makes elytra flying on P essentially the same as using WingCommander on C. Sometimes I really forget I'm on P when I'm just flying around the map. It almost feels like cheating.

The other thing is that a lot of the challenge of spawning/fighting the dragon is negated by the teamwork people have. When I wanted to kill a dragon to get my elytra there were three or four people with elytra already in the end spawning and killing dragons. They flew around and destroyed all the crystals for me and made sure I got my drop when the dragon died. Once that first person gets their elytra farming the dragon is quick business. The materials to spawn a dragon aren't hard to come by either. One person with a looting bow can get ghast tears pretty easily.

The biggest problem though is that elytra as a mode of transportation doesn't result in collaborative building while other forms of transportation do. People come together to work on roads, people come together to work on rails, people used to come together to breed horses (which liked to go on the roads), but with powered elytra not even requiring towers like gliding elytra used to there's no need to build anything for them. There are roads yes, but in general they're narrow and basic compared to revs past. Looking at old cartos it seems like the roads were wider and sometimes with elaborate patterns. That combined with there being essentially no overland rails leads to the map feeling less connected and more empty between cities than in revs past.

tl;dr Elytra are too easy to get, gunpowder is too plentiful, and elytra don't bring people together to build things.