I don't commute by bike so I never have to deal with people leap-frogging me in traffic but something I do have happen quite often is that I will be out and maybe see a cyclist in the distance and bit by bit, going at my own pace I will get ever closer.
Then when I am behind them, and maybe decide they are just a bit too slow for me to sit there for another 5 miles or more, I'll change down and up the speed a tad to get round quickly. As soon as they know I am coming round them, from nowhere a sudden burst of speed develops and I am left behind them again.
Now I don't mind that as such but 50 m down the road they slow down and I am left on their back wheel wondering should I match their speed or do I up mine.
If I step on the gas ( as much as a 58 yr old can anyway)
I am pretty soon putting in more effort than I want to, and guaranteed he will be behind me just
dying to show me how good he is.
I really don't care
And it is always blokes.
I'm not looking to race anyone but some buggers really do not like being passed.