Replying to my own question like on Stackoverflow, it could be that what wevorce does (from a business perspective) is create a new market (a cheap divorce where there is only 1 lawyer instead of 2, and less paperwork), and providing this market with a software solution that it builds and maintains.

Wevorce doesn't employ lawyers directly, it just acts as a marketplace between them and people wanting to get divorced without killing one another, and it takes a cut in the form of software licence.

So from this point of view there's no reason it couldn't scale indefinitely.