The are marketing gold bars as a "luxury item" not as an investment tool. But, they will know there is a lot of cash in London (Lots of Russians with shady pasts in particular) that doesn't want to enter the system through ETFs and bank accounts - so, let them buy the gold off the shelf no questions asked, from a business that has respectability and trust as its cornerstones of business.
Harrods wouldn't have set this up if they hadn't been approached already by prospective customers.
