The problem is the entire strategy of these spam advertising ICOs. There would be no problem if they only require 5 posts per week, but quality posts instead of 10 or 15 shitposts per week. There would be no difference for the visibility of the advertised project, but the forum would have around 50% less spam.
The explanation is quite easy: if there are more posts of every project, the visibility of these posts is decreasing, because they are very soon buried with other shitposts. If there would be less shitposts, the latest post would be visible for a longer time resulting in the same visibility. Instead of 2 shitposts immediately buried with other shitposts we need 1 quality post causing less spam for everyone.

But many projects are interested in having more posts per week related to other projects to increase the visibility of their posts. This is causing the spam problem and it would be easy to reduce spam by limiting the posts per week.