There's some really bad mouse accelerations built into desktop OS. For example Windows' mouse accel curve is an abomination and I really don't know how they came up with it. Maybe they threw a dice. [1] Comparatively a curve like [2] is much more suitable for gaming, as it essentially allows for precise tracking, small flicks with constant sensitivity, while still allowing for rapid 180 degree turns. Especially quake-like arena shooter benefit from this as you can play long range and close range with the same settings (Quake is where this kind of mouse accel was first implemented).

[1]

[2]