Simple. CLEVELAND ROCKS!
The best audiences can be found there and musicians feed off of that. Cleveland also has historically had radio stations that went out and got the concerts for us--like WMMS. Several artists have also broken out here (Springsteen for example) and so they feel loyalty or comfortable, I think. And a lot of musicians are from here--Chrissie Hynde, Joe Walsh, Trent Reznor, etc.
But I did see Paul McCartney in 1989 at the Civic Arena in Pittsburgh--he didnt make it to Cleveland on that leg of his tour (but did come a few months later, where he played to 80,000 people in Muni Stadium). 80,000 people rockin' out to "Let It Be", with a rain softly falling on a hot July night--I will never forget it.
Seriously, Cleveland has awesome audiences who are knowledgeable and passionate about music. They dance on their chairs and participate! LA has lame audiences that sit in their chairs and look bored as they wait to be seen by everyone else. I so miss Cleveland concerts!