Comment by nicoburns

It often is that way, but it's not for technical reasons. They're just poorly written. A lot of apps are written by inexperienced teams under time pressure and that's what you're seeing. Such teams are unlikely to choose plain server-side rendering because it's not the trendy thing to do. But SPAs absolutely can be done well. For simple apps (HN is a good example) you won't get too much benefit, but for more highly interactive apps it's a much better experience than going via the server every time (setting filters on a shopping website would be a good example).