The answer to the OP is that the line on what ATC is expected to deliver has to be drawn somewhere, and this is where it is drawn
Delivering the actual wind (in degrees
magnetic) on final is what they do. This happens to correspond to the way wind is presented in tafs and metars (but there it is in degrees
true).
If ATC handed out the c/w component, you would not know what any headwind or tailwind component was unless they gave you that as well, and that impinges on other obligations they have e.g. specifying a "gust" when the
actual wind velocity exceeds X knots, etc. You might have a "gust" on the headwind and have no "gust" on the crosswind, if their values happened to lie either side of X
And headwind is important because if it is say 40kt then you can expect an impressive amount of wind shear
