Even if we look at function and necessity, if we're honest, Batman stories in the last 10 years, as well as most Batman adaptations, proved that Batman doesn't really need Robin. Don't get me wrong, he can have Robin around, and it would definitely help, but he doesn't need Robin to function and not lose himself. And as much as I like all the Robins, I think that's an important take. An adult doesn't need a child to function, not as a crimefighter nor as a person, and a son should never be his father's emotional crutch.
I hoped the entire Tim story in UL 10 would elevate Tim to actually explore himself as something other than the forever Robin, with the understanding that he should be more than Bruce's helper for the rest of his life, but I guess that's not the case.
It's possible Tim would serve as a more grown-up Robin, but there's really no indication something like that would happen, and as things look right now, Tim seems to be going back to Robin mostly because his Drake take was a complete failure.