Browsers don't support it without config flags, so rarely. But there certainly is demand in visualization, games, medical imaging, "data science", etc.
(Also these apps are not necessarily written in JS, it's a compile target too)
Wouldn't that data be held in the language's kernel? When I load a 4GB file into memory in Jupyter, the memory is allocated in the python kernel, not the browser. Although I guess your point would be valid for iodide.io which seems to run everything in the browser.
Email services offer 50 gb of data storage for free. It's not so crazy that you'd want to load a substantial portion of that data into memory in an "offline mode" or while doing full text search across the database. Yes, there are probably ways to fit it into 4 gb, but I'm writing this post on a computer with 64 gb of RAM - why not write the next feature instead?
