Because it comes out of someone else’s pocket.
As the Godmother of an Autistic child, I can tell you that no sign will take the place of an adult’s eyes. To ask the community to pay for it, puts the responsibility elsewhere as well. I may be slammed for saying this, but I have seen many a parent of a child with special needs that have a HUGE entitlement attitude. They should always get some special treatment because of that child. Not all, Lord knows but some.
Did the parent pay for the sign?
flame away