Well said, Tig - same is true in my state of MO and in many other states also...
There are lots of step moms and dads who want the legal responsibility because the bio parent being terminated is a lowlife, doesn't pay support, etc - but still has say in major decisions like health care, schooling and the like. Sometimes there are legal reasons like THOSE to consider - in our case the bio dad never paid support, never saw the kids, but wanted a say in health care and schooling choices - and called my DH at work constantly as well. My DH wanted NONE of us to have to have contact with the biodad and therefore, initiated a way to make legal what already was. He knew full well that he would be as you say "on the hook" if there were a divorce, but we have two other kids as well so he would be "on the hook" anyway....He preferred to have the legal say, the legal title AND the responsibility for ALL of our children equally. You can say that the name/love/situation don't matter, but in fact, these are humans, so they DO matter.
And, in our state, the only way to accomplish both our legal and family goals was to eliminate someone who used power but no responsibility, and replace him with someone who wanted both the roses and the thorns of our children.
Stephanie