Hello Twink
He's not so ill with AD that he can't still do something but he just chooses not to.
Oh Twink, it is not as easy as that. I know it seems that way, but there is so much more going on.
YOU may think he can still do something, but he has probably lost confidence so that HE doesn't think he can do anything. He doesn't choose not to - well, not in the way you or I would mean - he may choose not to take another hit on his confidence, another realisation that he has lost so much.
It is classic that they come up with something they may think of as reasonable to explain their problem - anything that doesn't say "I don't think I can do it any more".
In time to come you may wish he was back at this stage.
I understand your comment that he is here all the time - reminds me of the famous saying about a recently retired husband from a stressed wife:
"I married you for life - not for lunch!"
It takes quite some time to come to terms with the aspects of this illness. Don't worry about how you feel - just make sure you are frustrated by the dementia, not by him....