Actually, I do think it is poor airmanship to take extra fuel if you do not have a good reason to do so!!!!
You could have burned 2 tons in the taxi, completely UNforseen, and still went flying. Yes, you would have to stop enroute, but that is the companies decision!!
The fuel policy is the same. You can commit (smartly) and never be in an unsafe position.
Provided the policy is safe and your decision making is sound there are no issues.
The bigger issue is what happens when 2 or 3 airplanes divert. Does the crew, all of whom are flying max hours, elect to go onto discretion or not?