Grimlock, Soundwave and Wheelie didn't have character, they had bizarre speech impediments.Agreed.
I'd go so far to even say that even the few who do (Bumblebee and Starscream) are really pretty much just cliche as can be in terms of characterization.
Let's face it.
The tech specs on the back of the boxes often had more character than an appearance on the show.
Is that why some of characters are so popular? Purely off their tech specs?