You can beset think about it like this: IPFS is decentralized in theory. That is, it is possible to achieve object/asset permanence without a single source. But it isn't baked into anything.

From a practical standpoint, IPFS operates much like a torrent does. Anyone can see the file, anyone can download it, and anyone can host it. But if the only host disappears, then for all practical purposes, it's gone.

When you host something on Pinata, other services (or other people) can "pin" the file to their own IPFS server. They have no obligation to, but they can. And since the files are cryptographically hashed, the "location" in the cloud remains the same. Or at least, there is a way to find it it's fingerprint should it exists out in the ether somewhere else.

With Imgur, if Imgur goes down that's it. It's gone. People can save a file and host it elsewhere to achieve the same thing as Pinata, but the file will have a different location and may have a different ID depending on how it's hosted. It may be hard or impossible to find again even if it does exist somewhere else.

Services like Pinata and IPFS are probably stepping stones. As a matter of practice we could simply hash all files, add that has to metadata and then make it searchable/crawlable. This is actually sort of what Google Images does is a weird way.