I think this comes down to the method by which the instrument produces the pitch.
Some instruments have a mechanical action that simply activates the object that sounds (hitting a piano string for instance) whilst others require that the player "sets up" the object to make a particular sound (putting your fingers over certain holes in a flute for instance).
In the first category you have the piano, xylophone, marimba, church bells etc. as well as tubular bells and (I'm guessing here) the cimbalom. I expect that there are many others.
In the second group you have the violin family, most wind instruments and, judging by other answers and comments, most brass instruments.
I suspect the Hornbostel–Sachs classification system would shed some light on this.