Because i do.
Of course there are plenty of times when i don't get DS, what he is trying to say or what he is doing. But when i don't get it i say it, and try another approach.
But more and more i feel like people either assume or pretend they understand him and vice-versa.
Like yesterday, i knew DS had gone with his nursery to the local library that afternoon, when i picked him up he started talking in his familiar jargon, i didn't quite got it the first time (although i got the impression he wanted to get his drink),
his teacher says -
"are you telling mummy where you went this afternoon?"
DS: "Yeah"
Teacher: "tell mummy then! whre did we go?"
DS "" looks up to ceiling with blank face.
Me: "did you go for a walk somewhere?"
DS starts to point at his trainers...
Teacher": We went for a walk and went to get some books at the library didn't we?" she was also signing walk, books,...
DS still looking at his trainers...
Teacher: "WOWWW!!! Are these trainers new?"
DS :"yeah!!!"
and it went on ...this was painful to watch, DS had abosolutely no idea of what to say, i don't think he even understood what the teacher was getting at.
Then after the teacher left, DS ran to the little chill cabinet to get his sippy cup.
This was just an example, this kind of things happens all the time with his speech and/or with some of his behaviours,...
people don't really understand him but carry on pretending they do and that DS gets it too when it is plainly obvious it isn't the case.