It's very simple. Because most of the projects you see here, are scams aimed to scamming the forum community.
That is one reason and another important reason behind creating token and doing ICO is because these new projects don't have the capital to back and build their idea so they seek funds from public and in return we get tokens whose value is later determined by how well the project performs and how useful the product is.
On another note, in a pvt investment pool which i participate in, most of the 10x - 500x gains projects have never ever seen the light of day on this forum
Yeah, not all the coins and tokens know about this forum and don't have the time to create and maintain a thread. But that said, Ethereum is like the biggest altcoin of all time and they created a thread here which means this forum is still one of the best ways to let the bitcoin community know about your project.