You're assuming that the economics that work for a mall would still work the same way when it's converted to "office space plus amenities". I know a few office buildings in Berlin that have a food court, barber shops/hairdressers, dry-cleaners etc. inside the building. And I doubt they're paying full price on the rent - they're advertised as amenities that make the office space more attractive, raising the price of the office space in the building.