Why are the public miners hodling so many bitcoin?

Many public miners are laser-focused on never selling the bitcoin they mine, and some of them own some of the largest bitcoin treasuries out there. Why do they pursue this hodl strategy, and how can they pay for costs if they never sell bitcoin?
Source: Production updates (Marathon, Core Scientific, Hut 8, Riot, Bitfarms, Hive, Argo, Bit Digital, CleanSpark, Cathedra)

The chart above shows the top ten bitcoin holdings of public mining companies. Some of them own thousands of bitcoins, and six of the ten largest bitcoin treasuries held by public companies are bitcoin miners.

Marathon is the largest holder with 9,673 BTC on their balance sheet, closely followed by Core Scientific, which owns 9,618 BTC. Core Scientific has more than double the hashrate of Marathon, so it should overtake Marathon's position as the top hodler very soon.

Why are the miners so focused on building bitcoin treasuries?

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