Thing is, a lot of guys shoot the same distance, at the same range, most- or all- of the time.
So, they zero at say, 100 yards, and never adjust the elevation or even the windage...
As long as the scope holds zero, there's never an issue...and the scope will "function" perfectly. It doesn't matter how clear the glass is, or how accurate the clicks are- they're never used.
Now, if you're a long range hunter, or target shooter, that's constantly dialing up twenty mils of elevation, and compensating for windage , that's when the precision and repeat-ability of better scopes becomes evident.
If that .25 MOA click is really .20, or is not exactly the same each time, any minor deviations at 100 yards quickly become evident when you multiply by ten when shooting at 1,000.