Why doesn't anyone bother flipping up the sights on an mp7.

[Gunmaster45]

Because in hollyweird land, you don't need sights. Everybody is either so advanced with a firearm they can pinpoint the exact place a bullet will go without aiming, or the magical magazine will hold enough bullets that they can spray and pray and eventually hit something. Plus it looks cooler with the sights down and most actors probably don't know how to flip them up.