Home Made angle plate for disk sander

[737mechanic]

This is a genuine question not a criticism.
Why are disc sanders popular? I have always failed to see any benefit over a belt sander. The surface speed varies over the face whereas it is constant with a belt.
I have a combined belt and disc sander but I have removed the disc because I could not find any application which the belt did not do better.

What am I missing?

I agree that a belt sander is nicer, to be honest, the variable sfpm isn't a concern but I would rather have a belt sander but all I have is the disk sander, I also have a bench grinder but the important thing here is even with a belt sander as long as you have a table with a slot which most belt sanders do then you could make an angle plate for it the same way.