Sometimes there are legitimate reasons to come up with schedules that are as accurate as you can make them, understanding that stuff almost always happens. Sometimes a project or some dependencies don't make sense if they can't be done by a particular date.
But, yeah, it's good advice in general. For most of the work I do (not programming), I have a pretty good sense of the minimum time I need and I almost always significantly pad that to accommodate priority interrupts or just so I can take a bit of extra time if I feel the task warrants it.
Sometimes there are legitimate reasons to come up with schedules that are as accurate as you can make them, understanding that stuff almost always happens. Sometimes a project or some dependencies don't make sense if they can't be done by a particular date.
But, yeah, it's good advice in general. For most of the work I do (not programming), I have a pretty good sense of the minimum time I need and I almost always significantly pad that to accommodate priority interrupts or just so I can take a bit of extra time if I feel the task warrants it.