It depends...

It is the job of an Engineer to determine what is needed structurally to hold a wing (or whatever) together, while making it as light as possible.

If the Engineer says to wrap a #" wide piece of Fiberglass around the center section, I do as he says.

Case in point...

Before the advent of newer kits, my dad and I used to mostly scratch build. Back in the late 80's, my dad got a Goldberg Chipmunk. When joining the wings, he didn't "trust" the thin plywood wing joiner, so he made his own out of 1/4" plywood, and made it much longer than the one supplied.

Having done that modification, he though he didn't need the fiberglass tape (which, under normal circumstances, he wouldn't have) but what he failed to realize was that the fiberglass also reinforced the LE where the forward wing mounting dowels were located.

The plane flew successfully many times, until one day when he did an outside loop. When the loop was just passed halfway done, and the plane was starting the up-swing, the dowels ripped right through the wing. needless to say, the plane (and engine) were a total loss.

To this day, I never second-guess an engineer.