There are reasons to play unrated even for a non-AP. Your daily average for one. Mail offers are calculated using your daily average. Suppose you are just on a quick trip, maybe going to play for a half hour, playing rated could actually lower your daily average and result in lesser future offer amounts.

I actually will use this excuse if pressed about playing rated. I will say something like I only have 20 minutes and don't want to lower my daily average and screw up future offers. And I have never had any pit critter push further because they know it is true. And since I play short sessions, when I get up 20 minutes later, it just re-affirms what I said.