Any% requires planning and thinking and adjusting your playstyle depending on how the run is going, which is uncomfortable for the human mind. When I was playing this game as a kid, I always went for max completion, so I was more naturally drawn to that category in speedrunning. Maybe others feel the same way.
120% has set routing for each level, with only minimal improvisation needed; and is relatively free of RNG. The better you are at 120% the better your time will be. Any% is pretty chaotic comparatively, as Jumpyluff explained. Many sections of the run can instantly kill it. It also ends with Twilight Skip/Rat Proxy so even a good time is never guaranteed to PB.
It also has to do with the fact that any% isn’t a very broken category in Spyro 1, unlike spyros 2 and 3 and plenty of other games. Part of the reason any% is more popular in other games is because in the historical speedrunning context, it made sense to use the any% approach to more people because the skips were so game breaking. That is less true of spyro 1; so the internal completionist in many gamers takes priority to many runners over the any% approach.
