Is there a reason why there isn't a glithless category for these games? Is it just because no one wants to run them glitchlessly?

In the end it probably comes down to the fact that defining a Glitchless category for these games that capture the true spirit of a Glitchless run would be pretty difficult, seeing as a lot of the exploits in these games derive from Damage Boosting from Bombs and enemies, which many would argue isn't a glitch, even though you can skip large segments of the game using these techniques precisely.

I've thought about it myself and I feel like the only way you could make the category different enough from the normal ones is to ban the really precise boosts (subpixel-based ones) but maybe allow some minor ones, but even then it wouldn't really change much for Seasons, and Ages would probably get really sluggish.