We've currently got the problem bigukg, that as there's fewer racers entering leagues, that you're left with 6 guys on a grid, and after the first season, the league either flops, or won't return until potential entrants return.
That's not saying "there's not as many lfs racers, blah blah blah", i'm saying that as things stand, people just aren't entering leagues.
For example my Stock Cup league peaked at 30+ racers this spring, but the autumn league only attracted 12-14 entrants. And I was quite happy we got that much!
Check out "RaceSim" as they've got a league starting soon "Formula XFR", (previously known as The Challenge Cup) which is a serious, clean league.
See the site at
http://fxfr.racesim.co.uk
hope that's help answer your question a little.