Aren't we talking about what paperwork the PNF does? In which case, it'll be the PF's job to be "operating the aircraft and missing the ground etc". However long a sector is, a fuel check should be done.
On a 25min sector we do one fuel check. Takes all of 10 seconds. It tells us how much 'excess' fuel we have, so that when looking at the destination weather, if it's crappy, we can straight away do a rough calculation of how long we can hold for.
I wouldn't really say that a fuel check is pointless and a detriment to the safety of the flight....