Gaming is actually a really bad example since as you say, you can't really on the clients telling you a time as it may be spoofed. Thus the clients times are always ignored, and thus time sync is irrelevant.
I'll say that in about 10 years of working on multi-player games, I've never once put a wall, or other absolute time on the wire for any purpose than just printing server time to the player for informational purposes.
If by such games you mean very specifically MMO's, then sure, I'll concede that time sync may be more valuable, but even then event serialization is normally done via an authority hand-off model that does not actually require time sync.
However, if you mean that all multiplayer games are typically played across "clusters of machines" and thus require time-sync then my original point addressed that.
I'll say that in about 10 years of working on multi-player games, I've never once put a wall, or other absolute time on the wire for any purpose than just printing server time to the player for informational purposes.