Where we live, at least when my boys were these levels, 4s all go to state and have their own meet. (No regionals for 4s.) 5 and 6 do not all qualify for state. 5 especially could be harder to qualify. 7 and up usually make state but not always Regionals.
As mentioned up thread, it is about money, the gym hosting the meet wants to have as many qualify as possible, so the qualifying score is set accordingly- so enough get through but in the case of very crowded Levels, not more than can be handled at one meet. If your gym usually goes to smaller meets, I guess crowded States can seem long, but in my experience States and Regionals are never the longest meets of the season.
Aside from it being a big and thus long meet, I do not understand the concern that a qualifying score is "too low." Competition is still going to be stiff for those at the top no matter how many athletes overall qualify.