Right - but SQLite handily beats the case where postgres is on the same box as well. And it's completely reasonable to test technology in the configuration in which it would actually run.

As an industry, we seem to have settled on patterns that actually are quite inefficient. There's no problem that requires the solution of doing things inefficiently just because someone said databases should run on a different host.

If you're going to run on more than one piece of hardware, something is going to be remote to your single writer database.

As an industry, we've generally decided against "one big box", for reasons that aren't necessarily performance related.