Agreed, and I hope it will become more popular. But right now, since you can't browse IFPS with firefox or chrome, and manual minting is harder than clicking a button on open sea, I wager private platforms will keep their appeal.
Maybe when decentralized service will do all the decentralized hard work for you, take your metamask, upload your content on IFPS, mint it, then let you sell it, it will take on.