The trap is the deliberate low point that holds a water seal against sewer gas — and it is where everything heavy drops out of suspension. Emptying it regularly means the debris never gets far enough down the run to cause a serious blockage.
Empty the contents into a bin bag rather than back down the sink, scrub the trap with a bottle brush, and check the rubber washers for perishing while it is apart.
Fitting sink strainers and a shower hair catcher reduces trap cleaning frequency dramatically.