It's worth repeating that when I started the topic I did emphasise that most fellow cyclists do return greetings, and offer roadside help if they think that it is needed, but, at the risk of sounding nostalgic (isn't that what this forum is about?!) I do think that cycling used to be a much more egalitarian pursuit and people were far less conscious of image and purchases. Many of the most passionate and committed cyclists rode on decades old frames, and expenditure was minimal.
Personally, I think that the significant number of fellow cyclists who blank you if you acknowledge them are far removed from that old egalitarian ethos, and subscribe more to the ethos of one-upmanship, but that's probably true of society as a whole!