I find some forums with no off-topic boards and one of the reasons I had read was to focus on the main theme of the forum. Maybe that's not a good reason because a forum admin should look at the benefit of a post and comment. Whether it is in the off topic board or not, a new thread means content that includes the subsequent comments. But perhaps profit is not the priority of the admin or forum owner. For those forum owners here, do you have an off topic board?
We do, but I don't necessarily disagree with not having one. I think far too much emphasis is put on activity in the pursuit of value. The most active communities tend to generate the least valuable content, and I don't see a point in supporting a community if it's not doing something with its activity.
We have general boards that aren't necessarily relevant to travel or languages. I can understand why certain forum communities don't have off-topic boards. I think it just depends on the forum niche.
On my forum, even though it's a gaming forum, 90% of our topics/posts come in 'off-topic' areas such as television, movies, general discussion, etc. I think it's necessary for any board/forum to have such areas, especially if you're just starting out.