I'm happy to report that most people usually do nod, wave, say "good morning", whatever. Which is lovely. It was actually this bunch being the glaring exception that made me bring it up.
If they'd been smashing along in echelon, then fine, I can understand not wanting to engage in pleasantries. But they weren't, and were bunched up chatting away (no issue with them being bunched up BTW, there was nobody to get in the way of).
I guess you're like me in that you think there's nothing lost by a little politeness. Maybe if we all smiled at each other more, we'd kill each other less. That's the old hippie in me, I think