The NFT is a pointer to content (pointed by a URL). If the underlying content at that URL changes, the assumptions about the original NFT minting / first transaction change.
Bundling a cryptographic hash with the original NFT assertion of content accurately describes the content the NFT was intended to be minted for.
Example analogy: an NFT is like a receipt for a baseball card signed by a player. If the NFT is minted when the URL to the content points to a baseball card for Player A (popular player rookie card), but someone hijacks the domain or the URL and changes the content of that URL to Player B (no-name player who only lasted half a season in the pro league), that hijacker has performed a misrepresentation/fraud. The hash doesn't prevent the content swap, but it provides assurance that the content still matches the original intent of the NFT minting.
But that makes the NFT less valuable. If the content at the url changes without the hash you still have a useful NFT. With the hash, your NFT is burned when it changes.
As a buyer I would want that one less. In the fraud case adding the hash damages only me.
Without a hash you just simply trust the issuer unconditionally? And you prefer this trust over a cryptographic guarantee the content, and thus the meaning, of the NFT won't change?
Why are people downvoting this? It's a very good point: the value of the NFT is the fact that it was minted by X. Nothing else really matters and what's stored in the NFT is just fluff.
You can't rebuild the image from the hash, but you can query various content-addressed stores for the image, potentially letting proof-of-space cryptocurrency systems do double duty as both verifiable resource commitments and repositories of blockchain external data.
I mean, it's still worse than not doing any of this lol, and that's the null hypothesis we should be using. Yes, getting stabbed is better than getting shot, but maybe stay inside and fire up a nice S3 bucket.
The real problem is any proof of resource scheme immediately becomes a grey goo where folks are incentivized to consume literally all that resource wether it makes sense or not. It has no negative feedback loop. It cannot make sense.
Also, because of market pricing of the tokens businesses cannot actually leverage it (as they don't want wacky prices that vary by the minute) so you're left with, as usual, illegal content, gambling, speculation and other misc crime. Basically why Filecoin has a small rack of hard drives' worth of stored data and Chia has exabytes and exabytes of garbage - or did, does anyone care about that one anymore?
It makes more sense to just store garbage if your goal is to run a neat little pyramid scheme.
See Moxie's tweet thread showing this experimentally: https://twitter.com/moxie/status/1448066579611234305