Yes, a good reason. Moderators could analyze the post before publication, and only after approval, let the comment go "into circulation". The first problem  this suggestion faces and which has already been mentioned is a huge amount of work that moderators can’t either do at all or they will perform it for a very long time, which will block the traffic of the forum, since the posts will have stand in line to be checked. And this process cannot be automated; it requires the presence of the human factor.

Secondly, it gives unlimited power to moderators. Only them decide whether to publish your post or not, without giving any warranty. Thus, the entire “business” on the forum suffers, first of all, bounty campaigns (I agree, maybe this would help to solve the spam problem to some extent, but I`m sure that we`ll find other ways to answer this question). It`s quite possible that corruption may arise on the forum: participants will need to write posts for signature campaigns, and the latter, in turn, need assurance that the posts will be written by participants. Only a moderator can provide these guarantees. That is, all issues can only be resolved through him.

I think this assumption contradicts the basic principles of this forum, which was built on the foundation of trust, mutual respect, autonomy and freedom of speech.