i've created some pictures and you can "own" them by sending me "money". on bitcoin, at least the picture exists on-chain, but the ownership is based on an agreement between users - not the actual bitcoin protocol.

on other blockchains, like ethereum, the picture isn't even on-chain - the nft just references an image on a server. and you "own" it on an insecure blockchain where rules can be changed in a whim.

and what is the point of owning any of these things? if you like the picture, just right-click and save. the only reason to own it is speculation while the developers promise a bunch of things that they have little incentive to deliver since they already have the money from the initial sales.

these are just the major reasons.