The problem is, that fps stays below 30 for 90% of the development cycle. Only in the last few months of a project everyone rips out useless code, debug code, debug overlays, loggers, extra network connections for statistic and performance servers,and finally you can produce a "nearly" final version of the game that doesn't have any debug code in - and only in that state you can see how it will run on actual hardware and start optimizing from there. So basically you arrive at a situation where you have 3-6 months before release,and you have this game running at 20fps on a console,and you have to somehow make it run at 30 or 60fps. Obviously profilers help with that a lot, but it's rarely a process which you can afford to be doing during most of development.