Don't get jerseys of young players who haven't made the team permanently. That's just a smart decision in general for any team. And sometimes a guy will change his number - Zubrus changed from 16 to accomodate Holik, Fayne from 29 to accomodate Clowe, and so on.
As for veterans and numbers, I agree, it's really not a big deal, and certainly Lou has let plenty of guys have numbers higher than 30 - no one seems to count Steve Thomas here but he was allowed to keep that one, and Michael Ryder probably should've been allowed to keep 73. Still, for rookies, it makes some sense that a young player has no control over that.
Never made much out of Steve Thomas' 32 because you had guys like Zdeno Ciger and Reid Simpson wearing 33. Pat Conacher wore 32 for a while too as a Devil (1988-92). Bernie Nicholls wanted to wear 98 when he came here, but Lou told him no.