I have never seen a line of wheel chairs waiting to use these facilities. I understand that there are not other options for these guests. I also understand that someone's DD8 should not be going into the men's room because urinals do not afford men any privacy. As long as the family usage of these facilities is not creating lines for disabled guests, people should not be so upset with family usage. Just MHO.
My DD uses a wheelchair and her wheelchair doesn't fit into the handicapped stalls at MK or Epcot (those parks are older and not as accessible). Our only alternative is the Companion Restrooms, so that means at MK, we only have 6 stalls we can use in the whole park.
On our trip this past March, my DD and I waited in line about half the times when we needed to use the Companion Restroom and almost every time we used one, someone tried the door or knocked while we where in there.
MK was the worst, where at times there were several people waiting ahead of us. That might not sound like a big deal, but since there are not many of the Companion Restrooms, we often had to go out of our way to get to one, passing regular restrooms along the way. Sometimes, we just gave up and went to another Companion one or to First Aid rather than wait in a long line. So, just because no one sees a line of wheelchairs doesn't mean that family usage is not causing people with disabilities to wait.
I don't know and am not making any judgments about people who chose to use the Companion Restrooms (they may have issues that are not apparent). It did appear that some of those people had other choices available to them (ie. a woman taking a 3-4 yr old boy into the companion restroom while the man she was with sat on a bench waiting for them to come out; a man who was in by himself; a woman with a little girl). I think a lot of the people using them were not aware of the lack of wheelchair accessible restrooms and just saw the Companion restrooms as nice Family Restrooms.
We almost always had to wait for the handicapped accessible stalls at Ak and the Studio, even when there were multiple empty regular stalls (the newer parks have wheelchair accessible stalls that a wheelchair does fit in, for the most part).
I'm not saying that they are only for people in wheelchairs. I realize that for some people (like the man with a DD or woman with an older DS, or someone alone with an infant or small child in a stroller), they are the best option. Just, please look at the other options available if there are any.