Because there is no real people behind such project, no whitepaper or businessplan. It's good to look through Scam ICOs especially on the team behind them.
You're absolutely right. However the tokens of many successful projects are below the ICO price or didn't give expected growth. For example Raiden. Other projects that collected hardcap have huge growth. For example Docademic. Although the price of the token doesn't always reflect the success of the project and often depends simply on expectations