Quote Originally Posted by NamelessNPC View Post
Isn't taking 10 or 20 something you can only do with skill checks?
Most of the time, yes.

However, it's also a convenient statistic simplification when you have a somewhat binary situation that you roll a d20 to succeed at. Taking 10 is just (slightly less than) the average result of a d20, and if you instead of Taking 20 just spent twenty times as long rerolling and rerolling your Tzocatl check until you get a natural twenty... well, statistically that's pretty much the same thing. Except you're not annoying the rest of the players as much.

Basically, allowing people to take 20 leads to less tedious gameplay. Taking 10 is more arguable, but given that Tzocatl encourages you to roll by giving you additional benefits for high rolls it kind of balances out?