Your headwind and crosswind component graph shows up on your Private Pilot knowledge test.
We actually do use this in flight (although we have a rough formula in our head, we don’t use the chart).
In flight it’s simpler to use what we call the 30-60 rule:
If the wind is within 30 degrees of your runway then it’s mostly headwind and only half of it acts as a crosswind.
If the wind is within 60 degrees of your runway then it’s mostly all crosswind, and only half of it acts as a headwind.
During the performance calculations, especially takeoff and landing distance numbers, we need to use this graph to get accurate information.