Logic behind 46 player active roster limit?

I have read here and in other places that the 46 nee 45 man roster limit does not make sense. "If you have 53 guys on the roster, why can't you use them all? Why set an artificial limit?"

This question has always made sense to me. I don't get the reasoning behind the limit. But, seeing as the limit survived another CBA negotiation, it clearly has some logic behind it.

So, what is it? Whether you agree with it or not, does anyone know the reason given by proponents of the active roster limit?