Your example may be true, but many sites are actually 100x100kb, spread over 3-5 domains (tracking, ads, etc) and browsers limit the number of concurrent requests to any one domain.

The recommendations here are actually pretty simple (though the image responsiveness can become complex) and are in line with Google's recommendations (https://developers.google.com/speed/pagespeed/), which are also pretty much the same as Yahoo's (http://developer.yahoo.com/performance/rules.html).

Ideally, you'd be doing JavaScript and CSS minification as part of your build or release process and push to a CDN, though some packages do it on the fly and cache the output. It's a surprisingly interesting practice.