There are rules about the minimum fuel, these rules are established to avoid that people would even take less.
These rules are fine if operational conditions are the same as the model used to calculate the minimum required, hence no other factors, adversely affecting the flight are present.
Minimum fuel means that you would arrive (after shooting an approach at your destination) at alternate with only 30 min reserve CALCULATED and taking into account that there are no fuel indicator errors and all parameters used to do the math are correct. This is basic knowledge everybody is familiar with.
Minimum legal and SOP are two different things.
Fuel policy can only be integrated into company SOP if you have a policy that is very elaborate like for example the one from KLM. In other words, when all variables that could reasonably be taken into account are present in writing in the SOP.
If you take 15 min extra you are only 15 min away from landing with 30 min in your tanks in case you divert.
Under certain circumstances, 15 min is nothing.
1. Cat I marginal or CAT II/III
2. Non Precision with a VIS that is lower than 6 x MDH
3. Significant WX
Then it is reasonable to assume that you may have to make a second shot. This has nothing to do with skill but only with luck.
15 min will not give you the chance to do that second shot.
Those that know what they are doing; cater for the cases were they may be unlucky.
Those that do not really know what they are doing need all the luck they can get.