I would say 75%+ of urgent care/ER visits could be avoided by a call/visit to a PCP (not just someone on call for your PCP) but I don't want to be on call 24/7 nor do I want to work evenings or weekends (although here I am at work so go figure).
I think ER care is good and pretty consistent where you go. Urgent care quality fluctuates much wider and I would bet I could avoid 90% of those visits if all my patients had my cell # but again that would be mental suicide.