Seems like boxing they want you to get basics of footwork before sparring...showing an eagerness to spar too soon might be seen as you being arrogant.
My first BJJ class I was kinda thrown into the fire...a black belt showed me to the side how to do shoulder escapes, but we were doing takedowns that class. I had to go up against a black belt and pretty had to rely on my instincts, football tackling and shyt..of course I got washed but as I continued going I learned some takedowns.
I get OP...while you learn hitting mits, some feel like they are actually doing something when they're going up against a live body. I think it's crucial to be sparring because you see what you're capable of, and what others are capable of.
Different culture though boxing,BJJ...
Day 1 in BJJ you're rolling, Day 1 boxing..it's not likely they'll let you spar...