When left to their own devices, personal care/hygene and even nutrition will go out the window.
I remember before my grandmother was in the facility, we went to visit her at home, and found very little food in the refridgerator, it was all food grandpa liked.
Grandma had been buying herself popcicles, and that's what she was sustaining hersef on, claimed it was all she wanted.
Mom went out and got some real food for grandma, and also got some popcicles that had more "substance" to them. She got ones made of pudding so that gram would get some diary into her, and some made with real fruit, so she'd get the nutrition in her from the fruit.