Right now if a brewery brews in their location but also has another restaurant/pub elsewhere in city they legally have to have a distributor to pickup the kegs, store them in warehouse for at least 24 hours and then deliver. And the brew pub is paying a 30% markup then on their own kegs.
They can sell the beer at the brewery without a distributor, of course, but if wanting to scale a business enough to make decent money it is ideal to have 2-3 other restaurants/pubs with the brewery beer, and they shouldn’t have to pay 30% markup on own product.