A legit purpose they have served is acting as a receipt that someone supported an artist. (Pictures of rocks that computers produce don't count.) What if this could be used to support Bitcoin development?
NFTs could be minted in different increments, (a green border means you donated 69,000 sats, a blue border means you donated 420,000 sats, etc) and they can serve as a "badge" that someone donated to support federated chaumian mints, Pickhardt payments, Statechains, or any project an open source developer is working on. Each project can have a different badge.
It uses people's desire to flex to motivate Bitcoin/LN development. They can be issued on Bitcoin in various ways, including Counterparty, Liquid, or maybe RGB or TARO in the near future.
If people decide they don't want to contribute to NFT Mania, they can even make the NFTs non-transferrable, ensuring that the address holding the badge personally supported the developer (although the possibility of resale could motivate more buyers).
What do you guys think?