my default answer is because music moves me.  at this point in my life, i dont even know who i would be if i wasn't a dancer.  one day last year (dont ask why), i completely lost the ability to dance.  i would be moving around while music was playing but none of my flow patterns, even the ones built into muscle memory, made any logical sense.  it was at that point i realised i had completely lost who i was.  fortunately it came back, but it made me realise how important dancing is to me, not just as a leisurely activity but as a part of who i am.

existence is random and chaotic, a series of events and phenomena that you have no real control over. look at the void for long enough, and your mind will try to rationalize away the chaos, but at the end of the day, the sky is just blue arbitrarily. liquid is a nice escape from that chaos, an activity where you can forget that shit is random, when you can make everything makes sense.

I flow because every once in a blue moon, I actually get a good feeling out of doing it, and equal as often I will have fun dancing with friends.

:D All great answers but I think what I'm wanting to know is...

Why do we flow... Instead of just popping, waving, or any other type of dance.  How come we all put so much time into this style of dance?  I agree that dancing gives us control over the chaotic mess around us, is a great source of play, and entertains others.  It seems like liquid really attracts some of the more unique dancers I've ever met.