Um... it's as "pointless" as any field.
What's the point in OoT's Hyrule field? There's almost nothing to do in it and it makes it take forever to get anywhere.
What's the point in the Great Sea? See above.
Twilight Princess has the only interesting and expansive overworld of the 3D games, but the most interesting field after TP's Hyrule is Termina by far, because it has intersting landscaping, a lot of things to find, and a variety of monsters to fight. It is small, yes, and it could have been bigger to give you more room to ride Epona, but how annoying would it be to waste your time running across a giant field when you only have 3 days? I think that making it small was a wise choice.