Mining has a cost in elecricity bills, asics heats and consume lot of power, to compute tge billions hashes it still cost something each time, not only buying the asics.
Each time they compute hash they take the risk to mine the block for nothing because someone else will mine it first, and waste the power used to compute the hash.
If you mine all day with an asic farm, it still has a high cost, if the blocks mined are not accepted, they still loose money.