I'd be happier if my browser made fewer requests, however small they may be. Even if they make up a tiny percentage of my internet traffic, it all adds up. Making computers do less unnecessary work is a good thing.

People are notoriously poor at predicting what increases their happiness; see Daniel Gilbert's book[1].

[1] https://en.wikipedia.org/wiki/Stumbling_on_Happiness

At Facebook scale, the sum of all those "304 Not Modified" responses is probably a significant amount of resources.

I'm not sure it's a good argument to take up the biggest companies and then tally up effects of a micro improvement. You could argue for all kinds of complexity increasing changes resulting in %0.01 efficiency improvements this way.

At my company, 304s account for 3% of our CDN requests.

304 requests are so tiny that you probably end up in the order of 0.01%.

Very few entities operate at "facebook scale".

But they still account for a lot of the Web traffic.

Think dropped requests. If you're operating with 99% packet loss like many people around the world minimizing the absolute number of requests can have dramatic impact on load times.

You can't do anything with TCP or the web in a situation like that.

What do you mean? I've operated at 99% packet loss plenty of times in the rural parts of Vietnam. The key is you can't use any of the websites or apps that are popular in North America / Europe.

The likelihood of even opening a TCP connection is going to be very low. For phase 1, stacks typically send 5 SYNs before giving up. So 95% of your TCP connection estabilishments will slowly fail due to timeout before you even get to phase 1 of the 3-stage connection estabilishment. To say nothing of actually transmitting or receiving any payload data successfully. Which you would have to many times to open a web page.