So at the end of the last few laps you will see a number of cars in the middle of the track stationary because they ran out of fuel?
That is a VERY rare thing.
Remember, drivers have the ability of turning down their fuel mixtures. So if the team detect (using their telemetry systems) that he car will run out of a fuel before race distance is completed, they will ask the driver to run a leaner fuel mixture.
Don't forget that before re-fuelling was introduced in 1994, cars would happily complete entire GPs without refuelling. So, the removal of refuelling isnt really a big deal.