When is SPA and when is MPA?

Question

Web development

I do not understand what the choice in favor of SPA or MPA comes from.
We do not take into account any SEO issues, etc., since these SPA problems are solved by server rendering.

When is it worth doing a SPA, and when is an MPA?
If we use React / Vue / Angular

For example Medium, cian - MPA (as I understand it)
and the same LinguaLeo - SPA.

What is the essence, how to choose and what to be guided by?
Googled, read, in almost every article everything rests on SEO.

Answer 1

Googled, read, in almost every article everything rests on SEO.

this has nothing to do with it at all, we use SSR and that's it.
In general, it depends on the development teams. SPA for the long term, in my opinion, is easier to maintain than the old fashioned way.
Also, the choice in the direction of SPA can be a large number of logic, which is rendered to the client, or a large number of interfaces that are interconnected. Or is it a site like Yandex music or VK, when the music plays, even if you navigate through the pages. Because the page is not refreshing. And the client gets only what he really needs without refreshing the entire page. This allows you to reduce the load on the server, but only when the audience is many many people.
The choice may simply be the love of the development team for one or another framework / stack. In my opinion, this is also normal. People write on React or back on php yii2, where should they take and switch to another stack when a new order comes? It is convenient for them, they like these tools, the processes are established, the style code is formed, modules or snippets ready for their work are already written, profit. This is the unity of the code base, which will allow you to quickly move from one project to another, because there will be the same stack everywhere.
If it's just a freelance site for 1 time, made it up, pulled it on VP (any other similar CMS) and gave it away (etc.), then no SPA is needed.
And if you have a development team, then in my opinion SPA is much better.
PS In our company, we completely switched to vue (nuxt.js) 2.5 years ago and did not regret it, the efficiency has increased and the transition from one project to another has become much easier. And the start of new projects was debugged by writing ready-made modules that were allocated in the process of writing past projects. Which ultimately allowed to reduce the cost (albeit not so much), but reduce the time to write the same modules.

Answer 2

It depends on the developers. As they see fit, they will do so. Somewhere there are not enough competencies, somewhere it turns out to be unreasonably expensive. And somewhere the interface designer decided so.
It's always a compromise.

Answer 3

Here cause and effect are reversed. Initially (!) It is determined what is better to do - SPA or MPA