"Aren't PhD students working long hours already? I really dont see where is the supposed additional slack they are having." They are - but I rarely impose my p

"Aren't PhD students working long hours already? I really dont see where is the supposed additional slack they are having." They are - but I rarely impose my preferences for when they work, don't check to see if they've accrued enough vacation time, etc. There's also slack that's not just "hours worked". A PhD student going down an intellectually stimulating but ultimately tangental rabbit hole that doesn't tie itself to a grant aim but might spawn a side project is something I'd encourage. I would not do the same for a staff scientist.