Generally reflectors have a tiny diffraction limited field of view. Refractors mostly are more forgiving and can tolerate minor misalignments and still give an acceptable visual image. I’m generalizing and most scopes benefit from accurate collimating. Refractor lens elements are generally closely spaced; reflector and compound designs often have large separations of their elements and basic triangulation over distance can cause visible problems at the focal plane. I suppose a reflector could be designed to perform with only a factory adjustment but affordability would likely be out of reach for the perceived benefits. Aspheric optical systems can have different tolerance envelopes compared to spherical systems.