Is AT&T’s decision final on not allowing side loads on Android phones?

My contract is up for renewal soon. And it’s worth changing carriers to get full use of the phone (will be switching from BB to Android). So, my question is: is this decision by AT&T final? And, yes, I know there are hacks to get side loading to work, but I refuse to be forced to jump through hoops just to load some software on my devices.

Imagine is Dell only allowed their customers to load Dell software. It does not make sense at all.

Come on, AT&T…