It's more like the only way the NFT can be minted is if an asset gets burned.
Otherwise if the money gets sent to the entity that created the NFT that entity can send themselves money to create infinite NFTs. By destroying the money we can show provably on-chain that nobody can mint infinite tokens for free.

We could think of this as the burned tokens being locked inside the NFT but it would really just all be lumped into @null on a technical level.