As always, there's two sides to it. Flight planning has to consider a fixed route including arrival, actual routing may be shorter due to ATC shortcuts, not having to fly the whole arrival, aircraft consumption figures calculated conservatively, etc.
Fuel burn statistics are trying to give some extra information on actual fuel burned over the last year or so on the same route or even flight number to give some sense how actual burns compare to planned burn. While this doesn't cover extreme weather or incidents, it may help in deciding on how much extra to take for route-related contingencies.
The thinking seems to be that an occasional diversion is cheaper than lugging around plenty of extra fuel all the time. While this is probably true from a commercial point of view, the drawback to this is that someone has to fly the diversion or taxi back to the ramp to refuel when there is a minor problem to sort out during taxi-out. Most pilots imho prefer not to be that someone.
From first hand experience, I tend to think that little to no fuel reserves are not conductive to good decision making. E.g. unexpected fog on arrival is taken much lighter with a couple of holdings worth of fuel in the wings than with zero extra. It remains our judgement how much of that lightness is warranted keeping commercial realities in mind.