I enjoy cooking and regularly make scrumptious meals for myself. Does this mean that I'm capable of running a busy kitchen? Of course not! So why assume that all software engineers can automatically run production services?
There's more to producing a restaurant meal than being able to cook one portion of the meal. How much of each ingredient do you need? What's in season? What's your budget? How varied is your equipment, and how experienced is your staff with it?
Running production services is no different. How many servers do you need? What hardware is on offer? How big is your margin? What infrastructure to you need to integrate with, and how experienced is your staff with it?
Software developers excel at writing applications across, mobile, frontends and backends. Working code is however only one part of a good product. Being able to juggle capacity planning, deployment, security, change management, monitoring, costs and the myriad of other aspects of running reliable services is a distinct skill set.
When it comes to having confidence in your production services, don't rely on someone who knows how to cook. Rely on someone with experience running a restaurant.