I think this is a really good point. It's worth adding that this has been much less of an issue in the past than it will be in the future, as until recently you

I think this is a really good point. It's worth adding that this has been much less of an issue in the past than it will be in the future, as until recently you could always count on increased clock speed. By not being architecture-flexible, your code is basically stuck with today's performance. That said, for some algorithms there's a decent chance that "today's performance" is about what we can expect 20 years from now, so maybe hand-optimization is beneficial.