Also since when exactly did websites have a mandate to economise to the scale of mobile data? It's always been edge case unless you are specifically targeting that.
Trends towards mobile-first have been a thing for a while. Especially in developing countries where mobile users outweigh desktop users.
Targeting desktop is slowly becoming the edge case for anything targeting a mass audience. Look at a lot of the recent high-value tech companies. Do Uber/Snapchat/Whatsapp/Instagram target desktop or mobile first?
Where are users in general spending the majority of their time? On a desktop/laptop, or on a phone/tablet?
Users, regardless of device used, are primarily on wifi and that is what is designed for. In modern countries most users don't really have data restrictions low enough to come into effect through websites so going into the future this will not be a problem.
Apart from laziness there is no reason for those websites to be so large.
Sure there's always room for an amount of optimization and good practice but it's insane to rely on that instead of fixing the problem. The growth in page size has been fairly linear and predictable.
The real headline here should be "German and US carriers cannot keep up with natural growth in technology"
You make it sound as if the natural growth in technology is what makes these websites huge. I run a web app, which is uptodate technology-wise. It has a responsive design with @2x images and @3x. It uses JS in a sensible manner. It's fast and easy to use. Top notch technology. Yet, the average request sums up to 200KB. And 60KB of that is a custom font.
This is not about the natural growth in technology, it is about 50-70% of the 2MB are entirely worthless to the user, because they are usually Ads, trackers, wrongly compressed images (ImageOptim does wonders here) and using 10 JS frameworks in parallel.
It's almost as if you're saying: See, img tags now support the width attribute, so let's upload a 10MB photo and just tell the browser to resize it to 100px, because technology.
So I go with a "those in glass houses" approach:
The only reason I can't see the terrible quality of your website's photos on my phone is that all the content is so damn small and zoomed out I can barely make out the text never-mind the picture pixels. I don't really want to zoom in because the shade of lime green you've chosen is so jarring it'll likely give me a migraine if it fills the screen.
I'm in the UK and the only network offering unlimited data is so slow you'll struggle to use more than 3GB in a month.
I've since given in and just paying through the nose for 16GB/month, so that I can not have to watch my data usage. (Un?)fortunately, the network is so fast I've found my data usage is already around 9-10GB/month, so I'm going to have to start watching that again soon.
See, what this boils down to is this: People use Adblockers, because they're tired of all that shit that's consuming their bandwidth (at least on mobile). Content publishers complain about people using Adblockers. But they're not willing to get the technical side of their content consumption platform right in order to accommodate their very visitors. They cry foul but are part of the problem obviously.
Unfortunately, I don't get to see what links to avoid (size-wise) before I download all the bloat and waste my bandwidth.
The growth of website size has been fairly steady, if anything the growth has flattened over the last year or so. It is up to the infrastructure to keep up with that.
In the last year or two we've had the introduction 4G with 2-4 times the speed of 3G and you expect to have the same usage allowance?
You should expect to have to increase you dataplan every few years (because technology) whether that cost is absorbed by you or your phone company is a conversation to have with them.