It already is. It's typical for mobile plans to be a fixed amount of high speed data, and once that runs out you're throttled to 128kbps. At that speed, many websites are not usable, forcing you to either pay for more high speed data or practically not have internet at all.

128kbps is more than 2x as fast as a 56k dial up modem, and while it's obviously not fast, back in the dial up days, the internet was still at least functional.

https://endtimes.dev/why-your-website-should-be-under-14kb-in-size/ while this is mainly about latency, 14kb web pages would solve problems for low bandwidth connections, too