A sensible scale is defined by the user's eyes, and most sites are not designed with impaired vision in mind. Web page text has never been set at a good size by

A sensible scale is defined by the user's eyes, and most sites are not designed with impaired vision in mind. Web page text has never been set at a good size by default, and most designers make it smaller than the default because they have good eyes and aren't thinking about visual impairment.