This is only true if you can hog the system. Application programmers often fall into the dangerous mindset of believing that their application is the only thing that matters and therefore it is ok to e.g. temporarily use all the memory a current machine can reasonably be expected to have.
Every single machine I've worked on for the last 15 years runs multiple independent applications at the same time, regardless whether this is a server or desktop. If one of the apps consumes an undue amount of system resources to the detriment of other apps, I'll be keen to look for an alternative. In the context of your post, if your app can now performs 2000 actions per minutes as opposed to 1000 actions before, it is highly likely that the 500 required actions will be performed using less system resources than before and this can be worthwhile although there is no measurable change in responsiveness.
So IMO performance does matter beyond responsiveness requirements if you consider resource consumption per action an element of performance. All the usual caveats (premature optimization is the root of all evil, profile before you optimize, developer time vs.optimization gains etc.) apply, of course.