For offline apps, WebSQL would have been awesome. Thanks to some ivory tower types at Mozilla we can't have it [1]. We got SQLite in a computer on Mars but apparently that's not enough to base a web standard around because some people think that It WoUlD Be BaD iF wE oNlY hAve oNe implEmentation! Oh noooo!

(This despite the fact that every Linux distro uses the same kernel and Linux hasn't suffered some sort of monoculture meltdown.)

[1] https://nolanlawson.com/2014/04/26/web-sql-database-in-memor...