I think this is probably the answer.
I’m brand new to Discourse as a Communites Engagement person, after moving to a new job role, but have discovered that I’ve actually been exposed to it a number of times as a user via a whitelabelled instance.
I’ll definitely be recommending Discourse as a solution in my networks in future!
Personally, I think the main reason is, that there is no obvious way for open source projects to get hosted. I would also love to use Discourse for my project, but the platforms make it hard and expensive.