Is there any monetary incentive for that? If yes, what are they?
This happens on PC all the time. Look at games like Titan Quest or Red Faction Guerrilla. The "remastered" versions of those games were just free for people who owned the previous versions. In the case of Red Faction, that's as far as it went. You get a new version with some post effects and the occasional new texture. With Titan Quest, they started making DLC again and released 2 expansions for the new version. Sometimes there's a financial incentive, and sometimes not.
Another example are the Bioshock 1/2 remasters. They were free for PC owners of the originals. Not really sure if there was any sort of financial incentive to do that, I don't believe any DLC was ever released exclusively for the remasters or anything like that.
There have been examples of paid upgrades, also. I know Hard Reset had something like a 90% discount off the remaster if you owned the original, so it was only a few dollars. Bulletstorm famously charged full price, with no sort of loyalty discount for previous purchases. Dead Island also didn't have a discount,
and they stopped selling the original versions, which makes sense, except that I own those, and my friends bought the only versions available to play multiplayer, so that didn't work out for us.
Anyway, I don't know why publishers release what amounts to a remaster/upgrade for free long after support is assumed to have ended on PC, but they do it pretty often. Probably about 50% of the time the upgrades are free.