Trading cards is a pretty good analogy. NFT's are a unique thing and will have value as long as people think it will go up. As soon as people no longer value them they will be worthless. They may retain value in the way a souvenir does but only if it is linked to something important to the owner. It remains to be seen how it will go once the initial enthusiasm is over with.
In my opinion, this is also being pushed across a variety of entertainment based industries (Art, Sports, Music, etc) to create a new variably valued asset with no inherent net worth that can be used for money laundering in the same way that art has been used for for money laundering by the rich and powerful for ages. For example. If I pay Bob $8m for his Painting of Elvis or for his NFT of Elvis we have exchanged something publicly for the $8m to provide a paper trail for the banks, the IRS, Customs, etc. No record of anything else that was exchanged under the table exists. Since the value is completely subjective it's hard for say it wasn't worth $8m. Especially if there is a large market of items constantly being exchanged for huge dollars.