Yeah pretty much what Silver said. The past 3 years or so, we'd done a good job at diving dates so that games didn't overlap but with the rapid growth in the player base the past 2 years and the arrival or commercially-driven fields on the scene (who want to host much more frequently) we had to adapt.
But with the increase in players came a diversification of gaming styles; the milsim crowd doesn't usually care much for skirmishing and vice versa, now we also have more specialized games like WW2 and Vietnam which are sorta niche markets that don't appeal to everyone... so why would a player be penalized on a weekend because there's a WW2 game on and he doesn't play WW2? There aren't enough "good season" weekends in a year to start doing that.
So we try to avoiding directly competing events (like 2 large milsim events, or 2 WW2 events) on the same weekend, but otherwise it works out fairly well since [example] milsims don't have to be dumbed down to cater to the otherwise skirmisher crowd, etc.
Similarly, asides from special large events, geographically distant areas (namely the Montreal area and Quebec City area) do things individually. The 3 hour car ride each way is really rough, specially since we've been having really hot summers that can make the day really exhausting. I did it twice last summer and I found it extremely taxing.