I was at a brewery a few months back when Biden was giving an announcement, this was before he dropped out of the race. I was mildly enjoying myself until some guy came in with his wife and just went off on Biden, and specifically orbited around "hunter needs him to stay in office so he can stay out of jail". Dude was wearing an FOP shirt so he's obviously an expert on knowing when felons should or shouldn't be in jail...
I bet another big reason is that he can hold rallies and get his narcissistic high. Has to be awesome for a narcissist to hold events where people are there just to hear him ramble.