The problem you're describing Exists in all engineering disciplines. You don't hire firm to feasibility studies, develop a design plan, do a materials bid, sub contract clearing and construction for your mailbox installation do you? Most people hire a dude hanging out at Home Depot and pay him a flat fee.

The risk and complexity dictate how much architecture and engineering are involved and with all things, businesses will try to get by with a bare minimum. The automotive, chemical, and other industrial sectors invest a lot in software architecture and enterprise architecture because the risk is so high. But even a medium size e-commerce platform has very low risk or complexity.