Personally I think it's because in CA the local communities are much more developed than in a lot of other places. In some states there is only one entity, whereas in CA there are several which are thriving. Jams are organized on a local level, not here on APK. On SFPK there's 2 big monthly sessions along with 14 (!) standing weekly sessions around the Bay, and that's not including BApk sessions which adds even more. Then you add PK Cali into the mix, which is largely SoCal, and there's a ton more.
There was recently a big jam where SFPK, SacPK, BApk and more members went down to SoCal and jammed with the PK Cali people and it was a big success, there will definitely be more of those soon.
While I'm typically focused on growing our local scene, it is a balance between local, regional, statewide and nationwide interaction. I think identifying the various local communities and setting up easy contacts is a good step to help facilitate visits, but I'm definitely open to suggestions on how to tie CA together more. State jams are definitely a part of that, but if you're talking about more online stuff then I'm not sure - I think in CA a lot of the online stuff is really just a representation of the actual communities and since those are large local communities the online stuff tends to stay local, and not on APK. I have been meaning to get on PK Cali more.
If you haven't joined any of the local CA sites, I highly recommend doing so!