Mainly because after collecting funds for further development, they are not working on the promised project. Resulting to the downfall of its price since there is no product. Some are working but the progress is slow and it is bad for the investors and they maybe think that the project is abandoned and I think having an active ICO group chat could make them less worry by updating them. But mostly ICOs are 90% fail since 2018 because of fraud, many projects to mention but that's it. It is because of the shit team who just want to get money from easily fooled people. So next time find a better project that won't left its investors until the end of collection.