Contributions have nothing to do with campaigns. Those who left the forum, there would be solid reasons; someone shared and someone did not share with the community. A few users passed away; sorry for them, and we miss their contributions to the forum. And a few people turned out with shady activities as well and eventually left the forum. I don't think any valuable users left the forum just for the gambling signature campaign. Because even if you search right now, there are a couple of users contributing to the forum who don't care about joining any campaigns. I don't want to tell any names; you can find them easily.
I don't like to create any controversy; those who left the forum, they have their own reasons. Unless they turned as a scammers or involved with shady activities, then I respect their thoughts behind the reason for leaving the forum. Valuable users are those who are active and don't like to join gambling signature campaigns; they might make fewer posts, but they still would contribute to the forum. Otherwise they won't be valuable right now; they were valuable once upon a time. I mean, just for the campaign reasons, any valuable members won't leave; they must have some other reason in their life.
Yeah, this thing has already been discussed above, and I agree with it. Everyone has some other things to do or has their other preference. But I shared my feelings here about what I feel and analysed. Because there are some users in my community that have not been here on the forum for a long time, and I know they do not join gambling projects due to some of their own reasons. But one thing I like in your post is that those users are the best community assets that still keep posting even though they are not enrolled in any signature campaign. They do post as to spend their time, or they consider it their duty that they should stay active whether they have a campaign or not.
I appreciate that you are not calling out those usernames. Yeah, I also know some of these users that are still active without having any signature campaign. They know themselves very well; they know their name and reputation, and believe me, many of them are big names in our BitcoinTalk community.