This is an incomplete and quite superficial view of what is going on out there, in my opinion. I've worked on plenty of projects where the assumption was that since the round-trip to the server is going to take almost 100ms that'll dwarf anything that's going to happen on the server itself, justifying poor choices that lead to potentially adding a whopping 100ms onto that number. These numbers only get larger with a larger perceived "Nothing we can do about it" budget as well, programmers often feel justified in doing just about anything once round-trip time grows, not understanding that they're just adding to an already existing problem.

On top of that: Creating software that isn't outright wasteful in terms of performance isn't even hard, it's just a matter of not doing ridiculously dumb things. The problem I've observed in teams I've worked with is that the majority of programmers don't even know what the dumb things are, and wouldn't know how to even approach making something that's halfway fast.

Edit:

Unfortunately I think posts like these are only going to make the problem worse, because now people are going to ask for voodoo solutions to performance issues, when the answer to their problems was usually just "Maybe stop creating wasteful intermediate structures and just walk an array like a sane person" in 99% of cases. The first leg of any optimization journey in the average programmer's code will likely net tens or hundreds of times faster code, and that's actually all people were asking for.

The knowledge required to make those changes and understand them is fairly minimal, but the kinds of people who have to create spinners for webmail interfaces, have their application add 150ms on top of whatever round-trip you have for processing things counted in 5 digits, etc., have never bothered to even learn those things.