The ol 'designers haven't figured out how to design efficient website' argument is rolled out now and then and it think it's time it was put to rest.
We're not on dialup anymore - there is no need to waste time on getting the most minimalistic (in terms of file size) anymore. Yes it's a nice to have, but no longer essential. Even mobile phones which are the closest to dial-up are heading down the fast 3G route.
It's the same as to why we don't need to program in machine code anymore to make the most 'efficient' program possible
I reckon most of these 'the internet is too slow' articles are just a media beatup. I'm yet to meet anyone who has 'slow' internet.