Since the Grappler Feat does exactly this:

You have advantage on attack rolls against a creature you are grappling.
You can use your action to try to pin a creature grappled by you. To do so, make another grapple check. If you succeed, you and the creature are both restrained until the grapple ends.

It's mostly only useful if you want to lock down movement without providing disadvantage to your Ranged allies (at the cost of locking yourself down too).

I can think of some other ways I'd like to spend an ASI for a grappler.