Is a house battery necessary if plugging in at campground?

For you dim bulbs that seem to think "budgeting" for a battery denotes poverty,well well Sheew!
Budget means to account for, to take count of.
It has nothing to do with the OP,s financial wherewithal.
I have to budget for my groceries, yet I can afford them just just fine.
I budget for a newspaper each day. That means that I keep track of the amount my daily paper costs,so I can anticipate that expense.
If the time ever comes that I cannot affor a paper I can adjust my BUDGET accordingly.