sorry but I see the op's point............and I agree. The op is NOT saying ALL nurses or the mojority of nurses are like this............just what they have experienced..............let's not be picky on exactness! lol!
Also......I have noticed similar stuff myself with my own child......non verbal so lots of people assume there is no pain...

and then you get the old "how do you know".ummmm.....because I do....
Also not to change the subject.........ALWAYS tell your patient what you are doing whether verbal or not................
I can't tell you how many times with my child they just come in the room and start doing stuff without so much as a hello..............and it's because she can't talk..........so the kid is laying there scared and shaking and no one says as much as one word.............gets my butt...........I always tell every patient what I am doing regardless of who/what.........it's kind of like second nature to me..........
But yes the pain thing definetly and the speaking to as well...........always put yourself or your loved one in their place & how you would respond..............