Have you ever developed an enterprise scale frontend applications optimized for conversion targets? It feels like you have not. You may ship your own code in a bundle, yes. All integrations come on top of that. That chatbot, tracker, A/B testing logic etc - all are loaded separately from your service provider CDN.

An user opening a web page is not expecting a full-blown app with multi-second loading times. If that happens, they bounce, and you loose revenue. Web is supposed to have very short time to first content paint and very short time to interactive, the shorter, the better, less than 0.5s is the goal. It can deliver that, if built properly. Many SPAs, bulky JS apps are built this way for developer convenience, not for end users. The only real use case for SPA is when you deal with a lot of local data. A spreadsheet, document or image editor, a diagram tool (but then wasm is probably a better choice).

You may say, you are not building enterprise grade frontend. But if you are small enough, you don’t need SPA either.