Probably doesn’t have auto defrag because God forbid the OS do anything useful for you without a hundred terminal commands and a two hour setup lest all the sweaty arch users barge in with claims of bloat and “reeeeee why can’t I just decide for myself”.
Most mobile operators in the UK have stopped with SMS limits (unless you’re on the really really cheap plans or PAYG). Guess people just don’t use them enough to warrant caps on it.