What is the reason behind the elderly not wanting to bathe?

There are many reasons. Some people with dementia don't want to bathe. It is one of the many symptoms of dementia. For some reason, the feel of the running water becomes confusing. Other people fear falling as they are getting in and out of the shower. Getting help can be embarrassing for them. Other people feel what is the use, because they aren't going to see anybody anyway. Still others feel they just don't have enough energy to do all the things that go into taking a shower. The reasons are many. If my father had had his way about it, he would have never bathed. In his case, I believe all of the above reasons came into play. But he always felt better after he had a shower.

Oh, one more thing. He is also cold all the time and after bathing he would be freezing. Mom's the same way.

My father stopped bathing, too. I think the reason was that it was too hard to do it and with his health issues, including COPD, he would actually get winded. He also told me once that he begins to hyperventilate when he takes a shower. He denied that he wasn't bathing, but it was pretty obvious. He is in assisted living now, and was resistant for a time, but now allows it. The ALF must give showers twice per week for each resident. He refused for a time, but they eventually just prevailed on him.