The reason I ask this question is because I have a friend that joined a boxing gym wanting to sparr and he been visiting that gym every week in training sessions for 3 months and still is told he can't spar.
the coach must deem him not technically proficient enough to fight. don't wanna put a guy in their prematurely only to have him get beat up. that's really all their is to it i guess, showing a good grasp of the fundamentals, and having people on hand in the gym that are the same level of skill as you. i was only matched with beginners at the 2-3 month point. if not, the better fighters were told to use only a jab against me, or go easy in some other manner.