It's not only that it's "not cool," but the outcomes of long hours don't match the expectations. The concept of "more person-hours in, more productivity out" heralds from the days of Ford, and strictly applies to individuals performing rote jobs on a factory floor (to a certain degree): tightening bolt after bolt, painting the car hoods as they roll by, nailing two pieces of wood together, etc. Human biology is adept at building up physical stamina when exposed to continued physical stress. During the alleged information age we have seen (time and time again) that our biology is woefully inadequate at building up mental stamina: we just get mentally exhausted (i.e. stupid).

Ultimately, if you pour more person-hours into software (or other "mind jobs") you should expect to get an inferior end product and/or diminished productivity.

Just look at Musk himself: sending out completely idiotic emails at 2AM. At least a portion of his behavior could be attributed to having completely diminished his mental faculties due to overworking himself.