There is a point.
You get to have the benefit of a one handed weapon and a higher damage dice.
This is very useful for something like a Monk who wants their off hand free for their bonus unarmed attacks.
Not to mention how a shield cancels out Monk and Barbarian's Unarmoured Defence so they'd be incentivised to 2 hand a weapon over using a shield.
It also enables the bonus from Great Weapon Master allowing the additional 10 damage while not necessarily needing to have the proficiency of a larger weapon (This can be very notable for say, someone using Phalar Aluve in a Dex build given that there is only 1 actual 2 handed Dex weapon in the game that you get in Act 3)