Earlier quoted context omitted.
> but low efficiency has no business- or environmental- downside, then why be efficient with it? But it has. Data transfer and processing isn't free. It works on electricity. You may think that a difference between 10KB (efficient) and 10MB (current web) is meaningless because resources are abundant, and it let you save couple hours of dev time[0] - but consider that this difference is per user , and you saved a coup…
I don't think people actually waste three orders of magnitude more electricity by loading 10MB vs 10KB - sure, that much more CPU time is used specifically on loading the extra data, but that would be a fraction of what's being used for all the other processing going on, and people don't just flip the power switch as soon as a page load finishes.
Yeah, they actually waste more in this case. The base cost is that of processing of content, which is linear with size (on a category level; parsing JS may have a different constant factor than displaying an image). But in the typical makeup of a website, just how much stuff can be in the 10KB case? Content + some image + a bit of CSS and maybe a JS tracker. In the 10MB case, you have tons of JS code, a lot of which will keep running in the background. This incurs continuous CPU cost.
> and people don't just flip the power switch as soon as a page load finishes
CPUs have power-saving modes, power supplies can vary their power draw too.
Or, for those with whom such abstract terms as "wastefulness" don't resonate, let me put it in other words: if you ever wondered why your laptop and your smartphone drains its battery so quickly, this is why. All the accumulated software bloat, both web and desktop, is why.