I'd say it's because the game has been out for what, 10 days ?
- Half of their patchnotes are for CRASHES. That's the priority right there : making sure everyone can play the game. And it's a good priority.
- As for mods : it would be pretty hasty of them to implement mods in the core game a week after said mods were created. They need to consider what make those mods good, or not, and analyze it. They'll do it, as they did with previous games.
- Modders are fast for 2 reasons : 1, they are amazing (seriously, M&B modders are crazy), and 2, modding a game is not the same thing as coding a game. Bug fixing is not the same thing as tweaking variables to make the leveling faster.
I can't wait for them to make the perk system work, but they seem to think crashes and performance issues are more important for now, and i can understand that.