Because a 2 lap sprint with high stakes for cars not designed for those sprints will either end in the same order they were in before, or a massive crash, as proved by this. In long races, red flagging 2 laps from the end ruins any good work drivers have done and drivers who got into a good position are at the mercy of someone else's stupidity - see Alonso's spin. We are past 75%, so full points can be awarded. We are past 90%, so any of these cars can be classified. This all smells of a way to hobble Red Bull and give a chance for someone to punt him off.
In a series where strategy and race-long plans happen, something like a Safety Car is to be expected, but a Red Flag is too far when it is for something as weak as the first two red flags we had today.
Racing is entertainment. Artificially closed up crashing is a joke.