While I do largely agree with you - isn't this is exactly the sort of thing that servers would be better at handling? For the most part, even if you load 1 GB

While I do largely agree with you - isn't this is exactly the sort of thing that servers would be better at handling? For the most part, even if you load 1 GB worth of numbers to do some processing with them, you'd probably only look at a summary of those numbers or some sort of aggregation. So your browser technically wouldn't have to load that information in JS, a server could do it and crunch those numbers presumably faster than a desktop would, and with a lot of these new client-app-like frameworks nowadays giving you near instant feedback, at this point we'd be arguing whether the "calculation engine" underlying the spreadsheet interface is on your local machine or on a remote machine.