You can set the weather condition in G2; such as wind speed, direction, gust speed, gust frequency, thermal activity, thermal frequency, fog, night, day, bright sun, cloudy and dark, actually quite a bit. Not as sterile as you might think.
Try setting those same variables in nature. YOU CAN'T! So in my mind...the very fact that you HAVE to set those variables, if you want to (try to) reproduce "the real thing" on the sim, make it just as "sterile" as I might think.
Having said all that, I do think the sims help shorten the time it takes to condition your hand to eye co-ordination. And that is the main benefit I believe.