I say hello to everyone when I’m on a bike, some reply, some don’t, it doesn’t change my life!
I was riding up from Peaslake on Easter Sunday on the road bike, I passed 3 guys riding together, they were all very cheerful, had a quick “lovely day for it” type conversation, then passed a chap who was clearly not enjoying the climb, he gave me a sort of grunty hello, then passed a bunch of about 10 guys on decent MTBs, they were spread all over the road, I sat behind them while they sorted themselves out, said thanks, wished them good morning, not one said anything. They went totally silent, having been chatting before.
I thought it amusing rather than anything!
Without wanting to pigeon hole people the ones least likely to reply is the radcoregnarly freeriders with body armour for sitting in car parks and at the top of trails telling everyone they’re stoked.
If it actually bothers you, I’d suggest SBZ may be onto something!