There's also the question of whose dime this caffeine nap is on: the employee, or the employer.
Each has an opinion and it's probably not the same opinion.
If an employer allows proper rest breaks, they do it on their own dime. If the employer doesn't allow proper rest breaks, it's still on their dime only in a way beancounters have more trouble counting.
In this case, there's also the question of where to nap -- not too many employers would like to replace office/factory space with a bed. I suspect only "live at the office" tech companies will do this, both as they already have so many perks and because they will benefit more from better employee concentration.