You have to consider most people probably work with snap on most the time. Thus it makes sense to have ‘Snap On’ only as I would hit it all the time without even looking to see if it’s on or off - because I want it on. ie, you press the key command for the work it is you are wanting to do without having to check if it is on or off.
I can never remember if I have it on or off, sometimes I think it’s off and press J to turn it on but forgot it was actually already on, now it’s off. then I moved a region, now I have to undo that move, and turn it back on. Very annoying.