Amazon is highly optimized for conversions on a single navigation. This is not representative of all web use cases. For ecommerce, I would agree with you. Th

Amazon is highly optimized for conversions on a single navigation. This is not representative of all web use cases. For ecommerce, I would agree with you. This is generally true of any site where a significant amount of the visits are load one page and then bounce to another site. SPA advantages don't help in your primary use case. In other use cases, which there are plenty, different sets of rules dominate. There are plenty of places where SPAs provide a much better user experience than MPA. I find SPAs simpler to do than MPAs if it fits the use case.