Ask yourself that the next time you're waiting for an application to finish or a webpage to load.

Right. Selfish me is more preoccupied with getting my job done quickly to get to other important things in life.

Update: Clarification: more development time saved allows even more tests to be written, profiling done, etc. which lead to better code quality in the long run. Considering runtime optimizations to be top priority above devel/maintenance time is detrimental.