Well you can't use a regular database, because it's easy for it to be hacked/shutdown, and if it's run by a third-party then even if you have entry in that database you don't technically "own" it. Turns out blockchains are a good solution for facilitating the idea of digital ownership, it can't be easily hacked/shutdown, it's run by the community, and if you own the keys to the NFT token that represents your ownership, technically you own that "database entry". You can easily sell/trade your NFT to others via smart contracts, transferring the ownership of the collectable/object they represent. The market has decided that NFTs are a good way to represent digital ownership based on the technical solution.
Want to see a successful example of the trading card world gone digital with NFTs? https://nbatopshot.com/