Because ETH has much more intrinsic value than AXS and the other tokens created by Axie Infinity. Why would they bother with pennies when they can take 100 dollar bills?

AXS's value is derived from a pseudo-feudalistic share cropping model called 'play to earn'. People in low income countries put up their real assets to borrow AXS tokens and NFT's to play the game to earn an income and farm items to sell to western players who can't spend all day grinding. Imagine if Blizzard designed WoW's monetization around exploiting all the Gold farmers?