I know you're in this for the satire, but it's less about the webapps needing the memory and more about the content - that's why I mentioned video editing webapps.

For video editing, 4GiB of completely uncompressed 1080p video in memory is only 86 frames, or about 3-4 seconds of video. You can certainly optimize this, and it's rare to handle fully uncompressed video, but there are situations where you do need to buffer this into memory. It's why most modern video editing machines are sold with 64-128GB of memory.

In the case of Figma, we have files with over a million layers. If each layer takes 4kb of memory, we're suddenly at the limit even if the webapp is infinitely optimal.

In fairness, this is talking about Figma, not an email client

It doesn't actually allocate 4 GiB. Memory can be mapped without being physically occupied.

Finally a web browser capable of loading slack