I agree 100% on the accumulation of some sort of loyalty points. To add to your frustration, no "free weekend" points accumulate when you credit to a Freq Flyer program, which I dont really understand... really because we PAY for those miles in the $.75 or $1.00/day Freq Flyer surcharge.
But anyway... at the end of the day its about the service I receive 40 weeks a year renting cars vs the 2 weeks a year i'm going on vacation, that makes me stay with AVIS. They've never screwed me, and I too enjoy my PC status.
If a $250 car rental is what I have to shell out on vacation to have peace of mind the other weeks of the year, its worth it to me.
My two cents.