I actually think that the associate countries are fearful about asking the ICC about the money distribution model. Probably there is fear that if they cause too many problems they are not going to stay on the scene for a long period of time. And another reason is the associate nations are not united. Or not getting enough money as they should be.
But at the same time, some other associate nations are very happy with what they are getting. So they do not want to make any kind of scene. If all the associate nations actually come forward together I think the ICC will have to take necessary steps about it. But again some associate teams are promised one or two series against the big four. And the associate teams basically do not say anything because they are very happy with only one or two series that they are getting.