CryptoKitties essentially sells crypto art NFTs to collectors on the Ethereum blockchain. However, the pictures of the cryptokitties are stored on the company's server, since the NFT merely represents ownership of the image. The artist/creator of the NFT always retains a perpetual obligation and right to store the image, whether it be on the NFT platform where they minted the NFT in the first place, whereas the collector does not have any whatsoever.
If the company's website or the company itself were to go down, then that cryptokitty would disappear. In other words, despite the collector owning the image via the NFT, they have no control over the actual online existence of the image. Even if they saved a copy of the image somewhere, the NFT can't be rewritten to redirect the link to the image, embedded in the NFT itself, to the collector's own copy since, upon its minting, the NFT's link permanently points directly to the cryptokitties server forever.
Now, think of this, people are known to dump $1,000,000's into these NFTs and other similar NFT collectibles. Do they not realize just how little control they have over their so-called "possession"? The fact that the image is stored off-chain on a server that the collector doesn't own or control, doesn't this jeopardize and undermine the whole idea of "ownership"?