> you don't need to talk about pointer events or flexbox or indexeddb or whatever
But missing functionality is a deal breaker.
* WebRTC - web peer to peer connection: Chrome & Firefox yes, IE 11 incompatible by design (bought Skype for 11b, based on it), Safari no (would be Facetime competitor)
* WebSQL - web relational database: Chrome & Safari (also 95% of all smartphones) yes, Firefox & IE no (declared dead by Oracle and MS devs (biggest SQL vendors), in favour of complicated NoSQL API IndexedDB on W3C mailing list)
* IndexedDB - complicated NoSQL API: Chrome & IE 11 yes, Firefox yes but slow (implemented on top of SQLite, refused to implement WebSQL API, FirefoxOS is the only smartphone OS with no SQL API), Safari yes but buggy
* WebGL - OpenGL 3D accelerated graphics: Chrome & Firefox & Safari(since iOS8) yes, IE 11 barely (old 0.9 instead of 2.0 API, few extensions)
* CSSRegions - desktop publishing stylesheet features like Adobe InDesign/MS Word: Safari & Firefox yes, Chrome yes but removed again, IE 11 yes but older draft
* ContentEditable/HTML editor - a bug free implementation would make MS Word WebApp & Google Docs obsolete: IE 11 yes (invented, based on Frontpage, old HTML4), Firefox & Chrome yes but bugs, Safari barely useable (especially on iOS)
So basically every browser vendor is guilty to some extend. Apple protects its AppStore walled garden, FaceTime and "Pages" word processor, Microsoft its Skype/Lync, Office and DirectX/XBox eco-system, Google its GoogleDocs and Hangout, Mozilla community has some sponsored devs from companies with their own agenda (e.g. against WebSQL API, while using SQLite in Firefox to implement NoSQL API IndexedDB).