The Web frankly just isn't evolving as quickly as mobile app platforms. HTML5 feels like ancient history, despite not even becoming a final recommendation yet and, imho, the rise of the gigantic javascript frameworks just shows the existing platform is sorely lacking... all it really demonstrates is the power of having a client you can push code to easily.
Where's my standard, secure browser UI and API for secure payments using my credit card? We've been using the web to shop for 20 years and it still sucks.
Where's decent standard authentication worthy of this millennium, let alone this decade?
Why don't we yet have date picker and other form widgets that actually work across browsers?
Why are bespoke markup languages like MathML and SVG actually failing or seeing less and less adoption?