Mr. & Mrs. only ?

Why is the only choice for the title of a married couple Mr. & Mrs?
(unless one of us is doctor--I wish)

As a regular friend of Common Cause I was very insulted to see that as part of a married couple my only choice when selecting a title for me and my husband was Mr. & Mrs.  Would it really be that hard to add Mr. & Ms. as a choice as well?  or how about for couples with different last names? (we happen to be a Mr. X and Ms. Y with children Z but we are married!)  and maybe singles with children would like say Mr. & Family or Ms. and Family. I won't even start with Mr. &  Mr. or  Ms. &  Ms.  How about a restricted blank so that some sort of title has to be entered but allow us to put it in ourselves.

I routinely answer mail on behalf of my husband and myself.  We vote together quite often and try to help each other keep up with what is going on.  I think it is good for our elected officials to know that there are at least two people in our household expressing a similar view.  Please fix the choices so that we can announce ourselves as the progressive couple that we are.

Thanks