The way it looks, over the past several years, about 1/3rd of LPFMs fail. Many say there are a good number of LPFMs that have been off the air by up to well over a year but never filed for a STA.
Here is the way I see it (my friend
@Michi is of course welcome to correct me if I am off anywhere in my observations):
For every Hans Laetz there are at least two or three LPFM operators who don't have a clue. They start out with a desire to be on the air and give the community programming that they can't get elsewhere, but few of them completely understand that licensed stations, regardless of size, have regulations to follow. As we have seen, even the ones who aren't flagrantly violating the non-commercial status of their license are not always clear about where the non-"crossable" lines are about announcements for local business supporters.
And I also believe that -- again, excluding the deliberate violators -- most LPFMs don't even have regular technical inspections of their facilities to ensure compliance. Unfortunately for them, "we didn't know we were operating at too high a power" is not an argument the FCC readily accepts.
Given just those two points, I conclude that the observation you made about silent LPFMs who have not filed STA requests is true. If they have trouble with the underlying regulations and also don't have a regular contact with someone who can keep them on the air legally, they certainly don't know that they have to tell the FCC if they go off the air for more than 30 days. The ones that have already exceeded a year will probably not even be noticed by the Media Bureau unless someone tells them, and those licenses won't be cancelled until they expire and no one sends in the renewal paperwork.
Add into that the operating expenses, even with a volunteer staff, and it is no surprise that the "glamour" of being on the radio dims considerably. So a lot of them fail ... sadly, because they probably shouldn't have gone on the air in the first place.