When people think great optics, it’s not usually in reference to magnifiers. Say, “magnifier” and people typically think of the traditional magnifier with a handle or, perhaps, a small pocket model used for a better look at a coin, twig, insect, print and so on. Don’t need great optics, here, and most people don’t want to pay a lot for this kind of use, anyway.
However, there times when optical quality in a magnifier is critical. One is a jeweler’s loupe, such as the Nikon 10x Jewelry, where optical color correction is of prime importance, since even subtle colors on a gemstone can affect value. Another is with a photographers loupe such as the Pentax 5.5x photography loupe, where resolution is critical for seeing fine detail on a transparency or negative. I have this one, not because I am doing work with photos, but because this Pentax magnifier does just as well when examining insects and flower parts as it does with photos. Like any true loupe, it is as its best when the eye is placed directly over the lens, but it can also be used as a conventional magnifier held at arms length (though a bit heavy and cumbersome).
Okay, I admit it, I also bought because I just love a well made optic and this one is a beauty.