[bzzzt]

Think of multi user databases where you want the latest version of the data. Local spreadsheets would be a synchronization nightmare. Also, web applications are seldom one single sheet, but an intertwined view on lots of tables combined with custom functionality you can't replicate easily in a spreadsheet. And that custom functionality needs to be updated once in a while. The web has become the easiest software delivery platform: you only have to update the server side. Even if a web interface is a bit janky it's a better alternative than maintaining lots of native apps (only Windows, Mac, how many Linux distributions?) or one of the cross platform toolkits that don't ever work 100% right and still require you to test on every platform.

[wolverine876]

Those are good points. I was thinking only of one use case, but obviously there are many more. It makes me think someone might try to create a high-performance spreadsheet-like UI for web applications. I've seen some spreadsheet-like UIs, but none I looked forward to using - though Google Sheets isn't horrible. (Probably, if it could be done easily, everyone would be using it.)