Seems to be a matter of taste to me. The current rage is for pastels to be very sketchy. I suppose that since it's considered the most drawing-like of the "painting" media, that quality is emphasized, just as watercolors typically go for transparency. (Wasn't Klee reacting to that notion when he spent so much time drawing lines with paint?) But pastels don't have to look that way, even retaining a fresh surface. I look at it more the other way around: as the most paint-like of the drawing media, pastels deserve to take advantage of their full, lush color, unlike those scratchy little colored pencil marks or monochrome charcoals
That untouched surface freshness is the reason pastels come in a few hundred colors. You can blend them to a fair degree, but you'll lose the surface texture doing it. So, if you need both a particular tint of a particular hue, and that surface, you have to have the color pre-mixed. (Optical mixing is the other main choice; layer works to a small degree, but soft pastels are pretty opaque.)
Razor blades are handy for scraping out overly-built up pastel, but it's better not to get that far gone in the first place. Regular erasers are for lighter chores.
Powdered pastels can be brushed, too, or washed with some water. Techniques abound.