There is a reason most jRPGs tie endgame fights with rewards that continue or wrap up your characters' progressions. For a lot of people the rewards making you stronger or providing you with more options on how to replay are part of the fun.
Often even the strongest enemy in the game will give you something that you can use to play around or to carry over into your second playthrough.

The only reason so many people here act as if expecting anything similar is so preposterous is simply because the designers in XIV always know best in their eyes. The truth is, if people really should be doing savage and ultimate "just for fun" and the majority of the playerbase doesn't raid, they shouldn't care if raiders get better gear that outperforms the gear non-raiders get access to in the next patch. The fear of making non-raiders feel "inferior" because of ilvl creep is very arse-backwards. What do they want that ilvl for if they don't raid? Expert Dungeon Unsynced?

Yeah no. I'm with the OP. If you do raids "for fun" then it wouldn't affect you if you also happened to gain more lasting useful rewards. And if you don't, you really shouldn't care. Literally no one would lose anything if that was the case.