Of course there are decent OFP calculations and my company has pretty decent ones as well. I still opt to usually take about 200-300kg extra in my regional jet for any unforeseen circumstances other than a full SID/STAR and the ~130kg contignency. I want to keep a few extra options open instead of immediately having to divert if you dont get the shortcuts you normally get, upper winds are not as predicted, destination airport puts a few planes in the hold etc.
It has helped to avoid diverts with the accompanying extra costs more than once, far outweighing the costs for the extra fuel.
If you are happy with min fuel and it works for you and your operation, no problem, no criticism. Just saying that the option for the PIC to choose should be there and not discouraged in any way possible as it sounds from the OP.