Web-tech is basically user-interface tech. Its super-power is that you can commit your GUI to be on the web, while the servers can be implemented with anything. The web-gui must have the most users world-wide, largely because all you need to install isss a wweb-browser and you get access to unlimited applications.

Any application can have a web-GUI, so why not have it, and they do, because that allows more people to use the app, with the standard conventions. Once you learn the basic functionalities of the browser (like back-button etc.) you can benefit from that knowledge with any app.

This starts to look like the good old OSI-model thinking. GUI is one layer, and like other layers it can be standardised.