Just guessing now but I also personally never use savegames. I always end up using localstorage.
(Correct me if I'm wrong) The thing with savegames are that they save absolutely everything. It's a complete snapshot of the current game state, like a savestate in an emulator. This can work but sometimes you don't want that. I'd argue that you almost never want that.
Lets say I have a game where I collect coins. When I die the game over screen shows and that's when I want to save them. But if I make a savestate there I will always load into the game over screen instead of ending up in the menu screen. Not to mention that you actually need to save a single number and you save an entire snapshot unless you manually exclude every single sprite/object. Also iirc you can't save variable A but not B so when you load, both A and B will be loaded but you don't want to load B because it's not something you want saved. Something you can work around... but you'll have to work around
It's a bit of an all or nothing solution and lacks some granularity imo. Sure will work in some cases, but I also get reminded about all the times I tried to savescum in a game and made a savestate that loaded me right into the deathpit :P