I believe a lot of fans in modern systems are for worse case rather than average case situations. As far as I know, there's nothing in the Dell et al. warranty

I believe a lot of fans in modern systems are for worse case rather than average case situations. As far as I know, there's nothing in the Dell et al. warranty that prohibits you from running a high-load system in a confined nook in a dust-clogged room with a high ambient temperature. So cooling needs to be designed to be sufficient even in pathologically stupid situations.