> “But in practice, constants really matter,” he said. “In the real world, a factor of 10 is a game ender.”

Working at a place who kept losing customers to a competitor whose software was less than 2x as fast as ours fundamentally changed how I view optimization and how I view constant overhead C. And crystalized once I saw how delivering steady gains milestone after milestone can buy a lot more goodwill than one fast and dirty optimization.

Speed doesn't matter if you're the only game in town (a monopoly). For everything else it matters.