Because, to use the same analogy, eventually that little puddle becomes a flood on it's own. At least, that is what I found. In my case I likened it to entropy, that is to say everything dying around me. It was, quite simply painful. When I realized that it wasn't so much everything around me dying slowly but rather myself, well, it was exceptionally easy to realize that not realizing I was a girl was causing me one heck of a hurt, and had hurt considerably much of my life. Simply, doing nothing, akin to walking by the puddle, was not an option for to me, that puddle had turned into a flood on it's own. Ignoring it was not an option.
That said, *shrug* "coming out" ended my engagement, and ultimately worked out better for me. I've not lost any family, an indeed any family that would disown me for this I don't WANT. It has, however, made my social paranoia/anxiety worse however.
Do what you feel you must, but personally, I find leaks need attended too before they demand attention.
*curtsy*