@Fiiily
Autommatic, Wordpress developers have done this because their main service wordpress.com uses the same feature. Today this feature is very popular if you are doing something more than a personal blog about cats. Nodebb has a ton of examples of how other forum services (like Reddit) were made. Maybe it will be their way too. In any case, I hope that someone will make a plugin that allows you to use one file base and easily manage many forums from one place.