Why do pro gamers play on small monitors?

Why do pro gamers play on small monitors? The thing with lower resolution monitors is that you can play on lower sensitivity(better precision) and with less mouse scrolling get to the end of the screen(cover more area). With that precision and coverage smaller enemies can be faster to hit than scrolling and shooting larger enemy.

The thing with lower resolution monitors is that you can play on lower sensitivity(better precision) and with less mouse scrolling get to the end of the screen(cover more area). With that precision and coverage smaller enemies can be faster to hit than scrolling and shooting larger enemy.