Because you normally need to use a framework + the front-end ecosystem and it's hard (as in: not something you can improvise, you need to be good at it and have

Because you normally need to use a framework + the front-end ecosystem and it's hard (as in: not something you can improvise, you need to be good at it and have years of experience in it). Many developers on the back-end think that the website should be a thin veneer over a service. When they find out they can't just hack on it, but they need to learn React/npm/react-router/table virtualization/some component framework they get irritated because they've always seen front-end as a "lower" discipline for "worse" developers. That said, a well-written SPA is able to express a class of web-based applications that, if written well, are indistinguishable from normal web pages (with anchors etc) but can do much more things than a traditional server generated web page. Since native apps are essentially living in paid, closed, walled gardens, long live SPAs.