Unprofitable to operate in friendly conditions*

If you can flip a switch and 10x the hashrate of a network, all under your control, and you don’t care about killing the chain in your attack, it may be a perfect exit for you if you no longer want to play the mining game.

There’s actually a mining pool doing something like this on smaller PoW bitcoins https://sharkpool.cash (not associated, just think it’s interesting)