It's not clear to me why almost any of these coins even need to be listed by regulated exchanges. Couldn't they just stick with BTCUSD and a few others then le

It's not clear to me why almost any of these coins even need to be listed by regulated exchanges. Couldn't they just stick with BTCUSD and a few others then let decentralized exchanges deal with crypto-crypto trade? Would they really lose that much business? I always assumed (though I've never actually checked, it doesn't interest me that much) that almost all of the shitcoins were like, the long tail few % of revenue for these businesses, and it feels like that's where all the risk is, since Bitcoin is generally recognised as a commodity. I mean, if needs must, spin off the shitcoin stuff into its own entity?