The problem is, of course, too many people abuse a relaxed commuting policy. Rest is a very important factor in safety and unfortunately some kind of rule is required even if it continues to be enforced in a relaxed fashion. I think if you're at your base 8 hours before duty and get yourself 6 hours sleep then you are sufficiently rested.
There's nothing worse though than being a Captain stood in briefing waiting for an F/O who's commute in has been delayed.