> Yet if I spent one hour making my app one second faster for my million users, I can save 277 user hour per year. But since user hours are an externality, such optimization never gets done.

Wait times don’t accumulate. Depending on the software, to each individual user, that one second will probably make very little difference. Developers often overestimate the effect of performance optimization on user experience because it’s the aspect of user experience optimization their expertise most readily addresses. The company, generally, will have a much better ROI implementing well-designed features and having you squash bugs