I do 95% of my shooting on 10-12x even with Tremor 3 reticles. That's out to 1100 yards.
Magnification ranges are like bike gears, at least in my mind. The sweet spot for image quality, eye relief, etc. is in the middle of most zoom ranges. So the sweet spot for a 3-18 is probably 6-14x. Likewise a 5-25 gives you 7-20x. So more magnification means a broader range and/or moving the range up higher.
The optical quality on most scopes, even that mid higher tier like a Mk5 is just not as good. Sure, a Mk5 3-18 on 18x has a better image/eye box than a Burris XTRII 4-20 on 20x, but unless you are going to a S&B, ZCO, etc. that top 10% of the mag range (maybe more) is basically useless IMO.
Plus you lose so much field of view you effectively can't spot your own shots. On a gas gun that is definitely something you want.
Again, just my 2 cents