Why do the interface objects (eg cursor, cmd+tab, swiping across desktops) seem completely unaffected by lag?

Whenever my MacBook Air 2015 experiences lag, most apps and interactions are slow to respond and often send my mouse into pinwheeling. However, the mouse cursor and trackpad shortcuts (four-finger swipe etc.) are completely unaffected like they are on a completely different OS. The mouse moves around the screen and everything is as flawless as it usually is. Very curious as to why this is so?