Peace of mind

Some algorithms in mining equipment are much smarter than humans. It is impossible to mine on a faulty cooling system on the equipment.
The newer one, yes, but for the S9, by using different firmware, you can disable the fan check and be able to run it without a fan. But the problem is, how can you get rid of overheating if you don't have a cooling system?
In the past, their way to bypass that issue was to have a DIY immersion cooling (Brains have this feature) aquarium as a sample with full of mineral oil. This one also helps to get rid of noisy fans.
I agree with you that it is possible to upgrade the firmware, but without knowing the basic temperatures of the chips and monitoring them, you could burn out the ASIC. ASIC S9 gives very little prof even with free electricity, and additional investments in immersion cooling make this idea unprofitable.