TCGs use fungible resources, though. Except for very rare cases like misprints or limited releases, two cards are completely interchangeable so long as they're the same card. I could maybe see Pokemon using NFTs because they're supposed to be your special semi-sentient animal friend, so making them non-fungible is a natural progression. They've approximated this with IV and PV, but ultimately you can still clone your shiny pikachu with hacks. An NFT pokemon could have a personal history on the blockchain (battles/contests won/lost, grooming/play sessions, parental/trainer involvement, regions they've seen, battle partners they've had, etc etc etc) which affects its behavior in subtle ways that simple numbers can't achieve. You could do this without NFTs using a centralized service, but I given the radical backwards and forwards compatibility of the games decentralization might make it a lot simpler to implement.

Note too that this is a strictly non-financial application of NFT. You could potentially exchange money out-of-band like you would in selling a card, but it doesn't require the pokemon cost anything. If I were to implement it, I'd probably avoid calling it "NFT" like the plague because it'd pull in cryptobros like a swarm of locusts and ruin the fun for normal people who don't want to pay $3000 for a Zigzagoon.