I think the argument that a high percentage of a particular flight or aircraft are entitled to priority boarding is not as prominent as it needs to be for two reasons.
First, those entitled to priority boarding are, presumedly, just as entitled to use the non-priority lane (although I'm reminded of a video posted on here a few weeks ago, I think from the TV show Curb Your Enthusiasm, where a First passenger is chastised for moving aft to use the Economy toilets). Simply, if the priority lane is too long, use the non-priority lane.
Second, and I think more importantly, is an expanded argument of one. You don't have to avail yourself of the benefit. You're free to stay in the lounge a little longer or linger at the bookshop and wander up towards the end of boarding. Some people are happy to be last on, probably moreso if they've only got their briefcase and a magazine to stow.
The important point is that the published benefit should be available, as stated; whether you use it or not is up to you but because it's published you expect that you will at least have that option. I guess it's a bit like the amenity kit (and pyjamas). Some take it, some don't. But you expect that you will at least be given the option.