Joe Biden is not jetting around the country to help fellow Democrats. There are two reasons for that:
The first and most in-your-face reason is that Biden is manifestly incompetent and extremely unpopular. Thus, Democrat candidates really don’t want to be associated with him in any way or even be seen with him. They (rightfully) fear that being seen (or tarred) as a “Biden Democrat” would be the kiss of death for them.
But second, Joe Biden is incredibly low-stamina. He simply is too feeble to do much barnstorming–he just can’t physically do it. Also, he has a strong tendency to say stupid things–and Democrat candidates want nothing to do with that. And that tendency to say stupid things, while historically always a part of the Joe Biden experience, is now exponentially worse given his much-more-than-creeping senility.
So the strategy for Democrats in anything but the deepest wacko red district is to just go it alone. They know that a Great Horny Toad who has a “D” after its name will get elected in those places. So they certainly don’t need the risk of having Biden there! Heavens no!