Why do dementia patients moan?

Well, it could be they have pain, either physical or emotional. Or it could be just one of those drive-you-crazy meaningless things they do.
I used to be appalled at the callous way the weepers and those begging for help were seemingly ignored in the nursing home or hospital, now I understand that sometimes it will continue no matter what you do.

I think sometimes moaning can be a form of self-soothing.

Some Who play Tennis scream when They Return Serve....Some Dementia Patients moan. Why ?
I guess Their Bodies are pushed beyond all endurance.

My mom has taken to saying "help me" a lot - when asked with what? She usually replies please or cries or says I don't know

They moan, sob, scream and many other things which are difficult to cope with but given their brain the control center of the body is not working properly it is understandable

After getting up for the umpteenth time I finally, and a bit curtly, asked my mother why the heck are you moaning, does something hurt? She says, "No, it just feels better when I do". Enough said.