If you say "Jump," I'll say...

... what's the point? I mean seriously, there are some phrases and expressions that I can understand. "Sleep tight." "Rule of thumb." "Raining cats and dogs." I get that the origins of these have a significance to cultural habits of the time. But to say something along the lines of "If you say 'jump,' I'll say 'how high?'" just seems to make no sense. What would the point be of jumping? Amusement? I don't know about you, but it takes a lot for me to WANT someone to jump. If I'm bored, watching someone jump is not at the top of my list. Sure, if there's a chance that someone might jump off of something (and survive of course, I'm not that mean) then it would be more of a question of what they were jumping off of. Also, if the person were to do more than jump I'm sure it would be more amusing. If they were to do a backflip or put some kind of neat spin onto it, then yes I may ask someone to jump. So it is not "how high" that should be asked. Rather, if I say "jump," you should respond with "from where and would you like it to be more than a jump?" I highly doubt that will catch on as the norm, but it's a lot more accurate.