It also means that if you have a building, and you put a sofa in the lobby, and carpets, and energy efficient light bulbs, and a pressure washer in the utility

It also means that if you have a building, and you put a sofa in the lobby, and carpets, and energy efficient light bulbs, and a pressure washer in the utility closet, and you hire someone to do security and maintenance (or contract it out to a third party service), and you set up some deal with Amazon to put lockers in the lobby — then you can sell all that stuff just by selling the LLC, and maintain all the contracts as you wish. Or, you can sell 10% stakes in the LLC to 8 different investors (keeping 20% for yourself), and not worry about eight 10% stakes in the building's pressure-washer. Corporations are basically containerization technology for ownership, and "a building" is a decent place to set a container boundary.