Needed, that's the wrong word. The bigger the better, it's a compomise about what you can comfortably do.
I just put fences at strategic points, so my 2 pairs of does, alternating, have the whole backyard, about 200m²,. They do a lot of digging though, but that doesn't matter to me.
My two house bunnies are free roam, in house and front yard, only restriction is that they have to be in the house at night.