Piano Keyboard
The idea of being able to play chromatically (all 12 steps within an octave), or even being able to play in different keys was not always as important in music as it has been for the last 300 years.
In the 1400s organ keyboards were very different. These "Short Octave Keyboards" had only C D E F G A B-flat and B. This allowed them to play both melody and accompaniment in either C major or A minor.
When keyboards became more chromatic in the 1500s, a variation of the short octave keyboard, known as the "broken octave" keyboard, started to be seen on the organs, harpsichords, and clavichords of that time. These had some split keys, where the front part of the key would play one note and the back part of the key would play another. Still these keyboards wouldn't produce a complete chromatic scale. However, since music was still written in the key of C, it permitted prime access to the most used notes, and the accidentals (the sharps and flats that would only occasionally appear in music) were relegated to a second (or third) row that was behind the prime row.
When the piano was invented around 1700 by Bartolomeo Cristofori, it featured the fully-chromatic keyboard that everyone is familiar with today. Composers like J.S. Bach and others became big proponents of playing music in all the keys, and also using all fingers when playing keyboards (including thumbs), which were rarely used prior to that time.