In Aaron Franklin's Master Class, he uses mustard on all the meats. But there's probably reasons for that beyond wanting the rub to stick, like getting a better coat of rub because he's so detail oriented, and not wasting seasoning.
When he seasons a brisket and is putting SP on the sides of the brisket, he puts his hand along the side the brisket and puts the SP in the palm of his hand and then pats it on to the side of the brisket. He says he does not want to waste expensive 16 mesh black pepper. And in his environment of smoking 110 or so briskets per day, every little bit adds up.
I don't use that much rub, but I hate to wash rub out of the sheet pan or off the cutting board where I seasoned meat. I want to use it all.
And I seldom watch any YT vids where a binder is NOT used, whether its barbecue or grilling steak.