I should point out, in case there might be any misinterpretation, that I was referring to fans related to general case airflow, not individual component cooling solutions! The latter can be absolutely critical!
And I say this as one who distinctly remembers mainframe style computers from my youth. When powering them up would result in, among many other sounds, the sound of jet engines from the fans revving up to blow cool air from under the raised floor into the cabinets. But of course then -- when 16K of memory was the size of three refrigerators -- the cabinets
were the components!