I agree that the first weeks of good weather bring out more riders than the last few weeks of good weather in the fall. And I agree that with the increase in numbers of riders, there is a decrease in politeness. Beyond that I dunno.
Sometimes I do suspect the more gear-oriented riders seem to judge other riders by their gear, and if it doesn't measure up to a certain standard, the rider I isn't worthy. The guys in lycra don't often wave at me, I think because I don't dress like them. But it's hard to tell what goes through their minds.
Such a limited reservoir, perhaps....
We did have a guy on carbon, in Lycra, stop to ask if we needed help on a flat at L'Ombra, on Rudi's flat, and 3-4 others asked earlier if we needed help, on Doc's stapled tire. Now, at Rudi's, it was purely genuine, but for Doc's, one does wonder what they thought when they saw 7 cyclists milling about one flat. I know I'd have been curious. I'm afraid BG may be pretty accurate; assisting other cyclists tends to get in the way of many cyclists priorities, and then when they see a steel bike, if they are of the newer persuasion, they also may not feel like there's much they can do for the poor old guy on the old bike....