Some people need more than one pair of glasses for different purposes. A choice for those with good distance vision or who wear contact lenses for distance seeing. Look up from reading or close work while wearing these glasses, however, and the world's a blur. If looking for inexpensive glasses to read a menu or theater program, these can fill the bill. But they're sprinters, not long-distance runners.
Many people also have astigmatism, which further complicates the matter.
Lots of lens designs are possible to meet varied needs. A contemporary example is the wide-band trifocal for computer users. These gradually change lens power from top to bottom. They're widely popular in Europe and gaining acceptance in the United States. These contain two prescriptions in one lens.