Honestly seems a little disrespectful of the equipment staff to do that in year one after a long time starter at that position left. Not sure if maybe they were out of numbers though.
I mean despite the numbers he put up, Carr didn't exactly leave on the best terms and while he put up some numbers he never really won anything there. Sure they did him wrong, but he basically refused all trades to ensure they would get nothing for him.
Beyond that, I guess I just never get the you can't wear someone's old number thing. In some other sports, like soccer for instance, it's considered to be honoring the other player by wearing their number. I guess I don't see how it's disrespectful. But, I do get that the culture of American football is different from other sports for some.