Before the 1880s, piano keyboards were generally smaller than today. Different sizes were available. There were pianos specifically marketed as being suited to women.
However, in the late 1800s, there was a push by piano manufacturers to increase piano sales by building large concert halls to attract audiences to performances by well-known European virtuosos of the day, such as Franz Liszt. These halls required larger, more powerful instruments.
The keyboard configuration designed for the late nineteenth century male virtuosos, with no consideration given to the needs of the rest of the population, is what we have today.
Josef Hofmann, a famous virtuoso in the early 20th century, had a Steinway made specially for him with slightly narrower keys…in fact the octave width was just 0.5 cm less than normal. (For further information, go to http://smallpianokeyboards.org/keyboard-history/) Expressed as a fraction, the keyboard width was 31/32 of the standard width, approximately half way between the DS6.0® (15/16) and today’s ‘standard’ keyboard with 6.5 inch octave. While his hand span was not particularly small, it was undoubtedly smaller than many other famous male concert pianists at the time though larger than the majority of adult women. It is interesting that even HE wanted to have ‘larger hands’. See the photo of his hands below.
Fortunately, over the last decade or so, one small manufacturer in the US (Steinbuhler & Company) has recognised and promoted the need for narrower keys. In particular, it is possible to take advantage of the full sound of the modern piano while fitting them with keyboards that are ergonomically suited to smaller hands. This “retro-fitting” gives the pianist 88 narrower keys that make no difference to the sound of their instrument. Other manufacturers that will make a smaller keyboard on commission include Laukhuff and Steinway. (See: Manufacturers & technicians)
Thus, gradually, but far too slowly, pianists are getting a choice. We don’t expect women, teenagers and children to wear men’s clothes or ride the same sized bicycle or ski on large skis nor, indeed, play exactly the same sized violin or cello. All of us have a choice of size for all those things, so why do we not also have a choice of size for piano keyboards?