Same reason that custodial shitcoin exchanges rake in billions... dumb capital that lacks the conviction to "invest" and instead chases the illusion of yield and arbitrage.
There's enough opaqueness in the variables to operate mines too, so its well suited to companies looking to separate fools from their money.
In a perfect market, Bitcoin would be secured purely as a byproduct of waste heat, from water heaters in every home etc.
It's currently secured instead by waste capital that is drying up, and there will be a major collapse of the mining industry as we know it in a swift liquidation event.
The distribution of mining equipment at wholesale prices, from datacenters to residences, will be one of the most bullish catalysts in Bitcoin's history.