These are Companion Bathroom signs. Two adults male/female and a wheelchair. No children in the picture as children's needs can mostly be met in a traditional bathroom. There are adults that need assistance of someone (companion) of the opposite sex and therefore it is inappropriate for them the take that person into the traditional bathroom. There are guests who's equipment can not fit into the handicapped stall particularly if they need someone with them. There are those with a disabling condition that requires them to have a sink in close proximity to the toileting area. There are guests who are older children but due to special issues not toilet trained and therefore may need some changing that can only be handled in the larger space.
There are many guests with special needs in the parks who NEED the Companion bathrooms, there are very few of them and it is disappointing to see guests using it because it's convenient or telling others they are Family Restrooms. My one exception is a Dad that is traveling alone with a little girl as men's room have urinals.
As a Mom who travels alone often with my 30 year old DS who is very disabled and can not go into the Men's room alone - these Companion bathrooms are our ONLY choice. There are not many of them, and if he has to go we often have to travel quite a distance just to get to one. It is difficult when the bathroom is tied up by those who don't require it and you can usually tell because when they open the door and see my DS waiting there - they become embarrassed, look at the ground, apologize and hold the door open for us. If I have my DH or other DS with me, we don't use them either, they take him in the regular bathroom. I guess until you are the person who really needs them - maybe you don't get how important they are to others.