The "big deal" is knowing a patch exists. I've probably got a few hundred PC games in total. Even if I were to set up an RSS reader dedicated to following the patch notes forums of all the games (which would be an insane amount of work and even the upkeep would be killer) It'd still take me crazy amounts of time to keep everything updated.
Steam also offers:
-one-login downloads (for other games as well as PoE)
-file corruption checking (for when mods go awry)