I have yet to hear a valid reason to even raise membership.
Just summarizing comments made by others on this thread.
This was directed at your assumption the number of members in USBC dictates the success of it. The USBC should be judged at the services it provides its members. If you want to receive those benefits, then you become a member. If not, you don't.
I agree having more members makes costs cheaper. But what do you think the cost to actively acquire one member is? It isn't free. It isn't cheap. Yet you want USBC to devote huge funds to try and acquire more members, and I am sure you would be so supportive of whatever method they choose.
You already have a group of people who look at league bowling in a more negative light than in the past in the proprietors. Bowling centers have been devoting more lanes and more time to recreational bowling and less to leagues bowling. (My first experience was Rock 'n Bowl in the 80s) This will inherently reduce league membership. But that is USBC's fault somehow.
Centers have to make money to be in business. My bowling center makes more money with 1/2 the house full of open play than it does on a full house league. My center won't even allow leagues to take the whole house anymore. So that is what the proprietor will try to achieve. Gone are the days of leagues paying the bills and open play being your profit. It takes a combined effort to stay afloat.