There's a time and a place for impact guns, including air, AC and battery. There's a time and place for hand tools.
If I'm switching to snow tires/wheels on one Saab with four bolts on each, the 3/4" socket and torque wrench has to come out of the 1/2"dr drawer, so grab the breaker bar and speed handle and I can do it with hand tools before the compressor airs up or in less time than I can string the AC cord, recoil it and rebox the electric gun. If I'm doing all three Saabs or the Ford F250 with 32 large lugs, one of the impact guns gets fired up.
An impact is also a great tool for running taps in holes in steel. With air pressure adjustment and the correct chuck, it'll be quicker and break fewer taps.
Pulling down core engines, it's impact all the way. Assembling engines, calibrated hands are the only way to feel everything is clean and going back together correctly.
jack vines