Because it’s more simple to copy-paste a G1000 in a flat pannel than fit 30 gauges.
Because its easy for them to built a G1000/3000 and stuff it in all the planes. I would like to see more conventional cockpits too.
Another way to look at it is Asobo didn’t hide the G1000 172 behind the paywall of a more expensive edition of MSFS.