> if a service returned a 4xx, it would trigger an exception in their front end code, and they didn’t want to tackle the complexity of handling potential errors from a bunch of different back end services

I’ve seen this when the frontend team is building a fat client/smart client/Single Page App but they really want to be building a thin client/dumb client/server-rendered app. Basically it’s a technological mismatch, and client teams feel a lot of pressure to build an SPA but don’t like/want/need the extra compexity that comes with it.