I felt the same, and have done both extremes. A cheery hello to an older guy one Sunday morning and, feeling a little awkward, really put the head down and really powered past on a commute the other morning to get it over and done with quickly. I think on the commute it's the latter, on a Sunday morning I'll exchange pleasantries. Suspect it'll be the other way round mostly for me though so I'll see what others do.
p.s. As an aside, well into a ride y'day I saw 2 guys up ahead on touring bikes and without thought picked up the pace to see if I could catch and pass them. Just as I got close behind them I had a blow out

. Either they had scatter nails on the road, or the fairy was trying to tell me to be more respectful
