I'm pretty sure he's always said Arc is a work in progress, and is not ready for full-fledged production use. I don't think he's ever recommended it to others.
I'm sure part of that is that he doesn't right now want to deal with people making requests for it. And having a userbase would mean that.
From what I remember of The Hundred-Year Language, that's pretty much what he said.
Off topic: I don't know how to encourage Arc. I don't even manage to follow the forum. What I know though is that I want Arc to exist. It's a huge mental relief to know it exists.
