Yeah, but I've seen projects using bootstrap, themes, extensions, and extras... in addition to jQueryUI & Mobile all loaded... as well as 2-3 versions of jQuery in different script tags.

That doesn't reflect responsible, light-minded development. Hell, load a couple of Airline website home pages... I don't think any of them are loading uncer 400kb of JS. that's for the homepage alone. Let alone the number of individual assets being requested (less of an issue once http/2 takes hold.. but still.

This. I have my own site slim and lean even with javascript (analytics) in there and it loads in 300-500ms. I developed a site for a client that was slim and lean and then it started. Sliders, full page background images, photos of random people, 3x analytics, this and that. It became a mammoth of 2-3mb and loading times of 1.5-3s.

When we tracked conversion the best converting page on the site was one made specifically for that and it is 100kb and loaded instantly. Two images and lots of text. They still insist on slow, beautiful pages elsewhere instead of making them convert as well.

I'm sure that's true of a certain class of developer. However, given what I've seen in the frontend & JS community in past years, I don't think there is a pervasive desire to make pages lighter. If it is, very few of them are showing that in the way they actually build things.

That's true in some cases, but there are lots of big company sites with no ad networks that are crazy bloated and slow. Some have trackers, but would be bloated (2,3,4MB+ over the wire) without them as well.

Doesn't Segment.io address such issues?