BTW, despite what Bluesy said about key, harmonica makers designate their 12 hole instruments by the name of the lowest note. The scale pattern is the same for all regardless of key. The few exceptions are the 14 hole harmonicas, starting on G but always in C, starting the pattern of blows and draws on the third hole; so-called Orchestra Tuned 12 hole C harmonicas starting on a low G; and the Chrometta 10, the only 10 hole C that starts on a low G.
Pianos are built in the key of C. You can play a C Major scale using just the white keys, no sharps or flats (the black keys). You can play in any key, but you gotta call it something. C it is. Playing all white keys is like playing a C harmonica without using the button. My personal opinion is that it's not worth philosophizing about.