When I was a Partner at DLA there was no restrictive covenant. The firm made a lot of lateral hires of Partners with followings and accepted that if Partners left then clients would leave too.
So why fight this reality?
People buy people.
Now firms try to impose stupid restrictions on Partners and in some cases actually prevent them from leaving at all.
I completely agree with Mark Brandon on this. It makes no sense.
Let partners leave: restrictive covenants are not helpful