Axie is built on Ethereum, meaning in-game assets (NFTs) are technically transferrable off-platform.
Vitalik (creator of Ethereum) attributed one of his reasons for creating Ethereum to Blizzard taking away one of his in-game items in World of Warcraft in 2010:
"I was born in 1994 in Russia and moved to Canada in 2000, where I went to school. I happily played World of Warcraft during 2007-2010, but one day Blizzard removed the damage component from my beloved warlock's Siphon Life spell. I cried myself to sleep, and on that day I realized what horrors centralized services can bring. I soon decided to quit."
Axie has banned the assets of players who have violated the TOS, so apparently they aren't decentralized enough to prevent Vitalik's origin story from reoccurring. Or is your point that those assets could be used in another game? Why would anybody do that?
Vitalik (creator of Ethereum) attributed one of his reasons for creating Ethereum to Blizzard taking away one of his in-game items in World of Warcraft in 2010:
"I was born in 1994 in Russia and moved to Canada in 2000, where I went to school. I happily played World of Warcraft during 2007-2010, but one day Blizzard removed the damage component from my beloved warlock's Siphon Life spell. I cried myself to sleep, and on that day I realized what horrors centralized services can bring. I soon decided to quit."