BA might not have designed it, but they certainly chose it for their aircraft. You don't have to have that setup, Airbus will gladly install a full size galley front and rear, cupboards, wardrobes, 6 full size toilets etc if you want them, it's simply that BA decided they wanted to cram the extra seats in instead. They were not forced into this config which pleases the accountants but infuriates the crew and customer, they chose it.