The ZIP-first approach assumes a postal code can deterministically resolve the rest of the address, which is rarely true in practice since many codes map to multiple cities or large geographic areas. Making it reliable requires maintaining comprehensive, frequently updated postal datasets or integrating with external geocoding services, which introduces non-trivial operational complexity. Additionally, deviating from standard address field ordering can work against established user expectations and may degrade usability rather than improve it.
In larger systems, what looks like “overengineering” can be deliberate risk management. In my experience, senior engineers do get promoted for simplicity but only when they can articulate the trade-offs and the future costs they are avoiding.