Not enough natural snow for it to be safe, most utah resorts also dont care enough to blow snow until they will make money.
Also, some resorts aren't on private land, so they have to wait for their lease with the forest to start.
Overall, its basically all about money, pc is really the only resort that could blow enough snow to open early, but they wouldn't profit from it and don't give a shit about locals. Also, it usually is barely even warm enough for pc to blow snow when they actually do open let alone in mid october, CO is much colder this time of year, hence they can blow snow and open.