[BrianOnHN]

Given that most public-facing websites want to benefit from SEO, it doesn't make sense to build a SPA for those websites.

I'd bet the majority of developers working on SPAs are doing so for internal dashboards/tools.

[jameslk]

You can render SPAs before the page loads, which eliminate any potential issues with SEO. This is how it should be done and the approach frameworks like Next.js take.