Because most folks are buying into coins that have pie in the sky promises. It's like saying hey give me 10 million for this product first and then I build it, but wait I'm paying bounties, promotions, and giving friends, families, 'advisors', shillers promotional deals that give them instant % gains compared to ICO prices. Then a dump occurs because, why not instant profit the 10, 15, 20% you just gained free.
If someone gave you a year salary to work (with no restrictions on actually working or not), would you even work? No, you'd take the money and travel, pay to speak conferences, submit yourself for pay to win awards, etc. Maybe slowly dabble in what you wanted to do for the ICO, but have zero accountability.
Most ICO's try the "utility" token route to bypass things, like buying Disney Land Cash with fiat. You're buying a worthless piece of paper and using it. If someone came to your house and asked you for $20 bucks for fake pizza cash, you'd slam the door in their face.
Most ICO's today seem to be a drawn out version of this, and finding the right team that really believes in the stuff they sell is rare. Not many people driven to change or work after you give them millions and no accountability. Pair that with everyone trying to "why no moon" after a week, insta red candles.