different experiences=different practices
some have different safety factors than others. some will get closer to thunderstorms than others. some will take the aircraft down to lower fuel quantities than others.
personally, i think it unethical to even consider taking a plane load of passengers anywhere close to a minimum fuel situation. and might be a bit silly to some, but i fly the aircraft as if everyone i loved was on board.
our plog shows at times less than 1000kgs for final fuel. my ZERO fuel is 2000. i will never plan to be in the air with less than that, regardless of the weather-- if that makes me a ******, then so be it.
i have personally seen UK alternates refuse to take any more traffic, after i have entered holding. so i use the most distant for planning.
and frankly, the number of times someone else hasn't diverted, does not overly influence my planning. when one loses a friend due to fuel shortage and resultant assymetric thrust on a twin engine aircraft, it brings it home like nothing else. that can happen on a 738 as well.
it would make a lot more sense to trim off the useless 5 sector a month freeloading management types than to trim off fuel for flight.