One factor is supposed to be hardware. There aren’t really any hardware keys that support BLS2 signatures yet (which is what Chia uses). Without that many of the biggest exchanges simply can’t list XCH. Smaller exchanges have more discretion to use workarounds. Whether the big names are wanting to list XCH or not I’ve got no idea.

Most exchanges that currently do support Chia don’t support Chia. You can’t withdraw Chia from there or even deposit. You can only trade the current price, but no Chia is changing hands. That’s because Chia uses BLS signatures, and exchanges do not support them (yet) since they are relatively new and most coins/tokens they support are just copy&paste ones, so they already have solutions for them.

KuCoin allows you to withdraw, but with 99% certainty, they are doing it manually using the official Chia client. That is not an acceptable solution by reputable exchange, so they must implement BLS support first. They would have a more significant incentive to do so if there would be more money in Chia or if ETH would finally switch to BLS signatures as well (but that’s a never-ending story).