The actual content of the NFT, such as a piece of art, is rarely stored on the blockchain. The reason why the content (such as a JPG, MP3, or Gif) of the smart contract associated with the actual NFT is stored on the web and not the blockchain is because of the size and cost. So you don't really own a piece of art. You own a piece of metadata describing some art that is stored on a centralized server. Those servers will, inevitably, eventually go down, be hacked or bought out so the owners of an NFT will, in the long run, own nothing but some metadata pointing to a defunct site.
The content was never meant to be stored on the Blockchain. If it did, most blockchain networks would be so bloated, the average person won't be able to use them for day-to-day payments. What's added to the blockchain is only the smart contract (in some NFTs) and its corresponding hash value to prove ownership. The ideal way to decentralize NFTs would be to store their content in a distributed file system (like IPFS or ETH's Swarm), but not many people aren't that tech-savvy enough to do this. I wouldn't say NFTs are a scam, especially when the trend is beginning to blossom. There are some NFTs that are being sold by legitimate companies (eg: Pringles, Nike).
The future consists of full digitalization of our lives, so NFTs make the perfect replacement of physical items/collectibles. It'll be up to developers and the community as a whole to come up with real use cases in order to spur adoption of NFTs worldwide. The case of LUNA/UST was simply an irresponsible move from the project's team. You can't compare it with NFTs since it's apples vs oranges. What the future holds for the NFT industry is a mystery to all of us. As long as there are legitimate use cases for it, nothing else matters. Just my thoughts