Ideally, any forum / group needs input, the more varied the better in order to get discussions going. Many people join forums (as members) for different reasons, such as support for a product etc., to be able to read (or enlarge) information that is not available as a guest and, of course, to post comments.
Some people may not post at all. Some people may just post once or twice (especially in a support forum), some people may post regularly. I have done all three on different forums over the years. There are also the guests who either look at a forum occasionally or on a regular basis. I do the same.
In a way, a forum is like a vicious circle. It needs posts to attract readers. The more posts, the more readers and more likely people are to reply. On the opposite side, the fewer post a forum gets, the fewer readers etc. Posts that are controversial are more likely to attract discussion.
From the start, the forum was designed to be open to most things, with members able to say whatever they wanted. Censorship would only be used when absolutely necessary and that would be done on an individual post basis rather than by subject or company. It was hoped that members would use common sense when posting. Controversial posts would be allowed subject to above. As you say, here it is nice and relaxed, and I think people appreciate that.
One thing I do find with forums etc. is that they can sometime take up a surprising amount of time. On the amBX forum (now defunct) where I was a moderator, I would answer questions and give support on the hardware side of the Philips amBX system. It was not unusual to spend perhaps 15 - 30 mins on a reply or even longer if it was a lengthy one. There are about five groups / forums / blogs that I read through every morning and even just doing that (with the relevant sidetracks and links that may be involved) can take an hour. Luckily, I've managed to avoid joining an social media sites such as Facebook and Twitter which would be even more of a distraction. The time involved may be a reason why some people don't always bother with a forum.
What is needed is more people to post, preferably with a few varied subjects, and get some discussions going again. With the amount of members that the forum has, I'm sure that they between them they can start off some interesting threads.