Why are villains much harder to defeat than heroes?

[Roogle]

I know that for a fact, because I also play Street Fighter, and there are certain bosses that are very hard to defeat, but they're not as user-friendly when you play as them; typically, Akuma, Ryu, and Ken are at the top tier, but out of those three, Ryu is the most user-friendly.

The tiers in Street Fighter are based off of tournament results from people playing each other competitively.

Are you taking that into consideration when you say that the villains are more powerful than the heroes? I think some of the villains are actually pretty low tier on the Dissidia side of things.