I worked for a few months at a convenience store(worst job I ever had), and my experience was that the only people who usually got upset about getting carded for booze or smokes were the ones who were underage.
I'm 35 and I still get carded occasionally. I always thank the clerk or waitress loudly and sincerely and tell them they'll never hurt my feelings by asking to see my ID for a beer. I don't know why the seller should be embarrassed, or the buyer should ever get upset if they're old enough(although I've seen a few jerks who do get bent out of shape), and the older, the better! ;)
A couple weeks ago. I'm 45, with a greying mustache fer pete's sake! I told the clerk, I've got hats old enough to drink.