Not all, but mostly it was because new coins doesn't have their set goal or plan, all they want is to be listed on exchanges but even they got listed they will end up being worthless if they don't have any value in crypto
New coins/project mostly only for quick bucks or fast money, the owner just make a simple project and bounty, and hoping investors invest the project. The thing is when the coins listed on exchange, the price will be small and worthless, because no one will buy the coins, only sellers.