Comment by blablabla123

It's not that SPAs cannot handle that but it's rarely a requirement.

I've once launched a product on (early days) Google App Engine and it was unusable as purely server-side rendered website because sometimes it would take ages to load or worse an error would come up eventually. With AJAX it could be solved and failing requests could be repeated. It's a pity that this is rarely done but it is of course possible.