Ok but why ? And what can we do to improve things? Promote maintenance, but I think one of the issues is that you can show something new, it's much more difficult to show that something could have changed (failure, difficulty to grow), but didn't.
To the extent it's in your power as a developer and a team member, don't tolerate low-performance code from yourself or your co-workers.
In my experience, a lot of performance problems boil down to really stupid problems, like simple code using the wrong data structure out of convenience (e.g. linked lists instead of arrays for lots of randomly-accessed data), or structured in a bad way (e.g. allocating a lot of small pieces of memory all the time). Often times, there are cheap performance wins to be had if you occasionally run the product through a profiler and spend couple of hours fixing the most pressing issue that shows up. Couple of hours isn't much; there's enough slack in the development process to find those hours every month or two, without slowing down your regular work.
I agree with your point of developers being responsible for the performance.
But I have a different experience (probably because we work in different areas):
Most the performance problems of the products I ever worked were purely systemic.
They boiled down to technologies and architectures having been chosen for "organizational" rather than technological reasons.
And "organizational" is in quotes because sometimes it was just blackmail: I worked with two developers who quit in protest after the prototype they wrote in Scala was deemed not good enough and dropped for... being too slow, ironically.
This has been a major frustration for me as a UI developer on the current application I work on. The UI is often hamstrung by how the backend API was implemented. There are frequently cases where we stitch together pre-existing API functionality to make something work in a far-from-ideal manner just because it would take longer to do it right and no one is interested.
I've seen a similar thing happen. It all started with good intentions, like only having simple endpoints that do "one and only one thing".
In the end the backend was pure and beautiful, but the the frontend devs had to perform joins in the the client and make 21 API calls in a 20-item list and then everything goes to hell.
