The modern piano keyboard, with twelve keys per octave, has become so commonplace that we aren't used to seeing alternative versions. The modern keyboard is simple and efficient, but it is far from the only possibility. Imagine practicing scales on this keyboard with thirty-six keys per octave, spread over two manuals.
The above picture is a modern version of Nicolo Vicentino's sixteenth century extended meantone harpsichord, the archicembalo. It is just one example of the various keyboards that had more than twelve keys per octave, so the performer could choose intervals that were more purely tuned for the key he was playing in. (Our modern twelve tone equal temperament uses equally spaced intervals that are different from purely tuned intervals to make it easier to modulate from key to key.)
This tradition has continued to the present. Computers and electronic keyboards make it easier to experiment in microtonal(anything other than twelve tone equal temperament) tunings, ranging from the historical to the exotic to the highly experimental. Alternate keyboard layouts for acoustic instruments also continue to be made as can be seen in the following pictures.