Every company runs certain business processes, either documented or not. These processes can be simple or complex, depending on how big and complex is the company. Collection of processes comprises certain structure. To name this structure ‘architecture’ or not, is a matter of taste.
Suppose you decided for a short trip outdoor and intend to pitch a tent for a night. With some skill and common sense, you can arrange pegs and pins, spread a canvas and have a reasonable shelter for a while. Should you hire an architect for this purpose? Probably, not.
Suppose now that you decide to build a house. You can affordably buy some bricks, tiling and cement. With a bit of luck and advise you can compose these into a sort of walls and a roof. However, there will be a risk that the construct will eventually collapse right on your head. Detailed architecture and professional builders are always advised to avoid a trouble.
Enterprise architecture is a comparable challenge. If you keep a stall, drawing an architecture for it might be an overkill. But running a decent corporation without well developed process architecture will eventually lead into disaster. Remarkably many skyscrapers on a business landscape collapse just by missing their architectural foundation.