The real answer to the question isn't technical. Local-first apps haven't become popular because companies recognize that their value comes from controlling your data.

In a talk a few years ago [1], Martin Kleppman (one of the authors of the paper that introduced the term "local-first") included this line:

> If it doesn't work if the app developer goes out of business and shuts down the servers, it's not local-first.

That is obviously not something most companies want! If the app works without the company, why are you even paying them? It's much more lucrative to make a company indispensable, where it's very painful to customers if the company goes away (i.e. they stop giving the company money).

[1] https://speakerdeck.com/ept/the-past-present-and-future-of-l...