Altcoin scam comes from coins that are mined before a project is launched, the coins are sold before listing the coin on exchanges, the developers can leave the project on the day it supposed to be launched and take away all investor money. Some can even just list the coins and sell all their coins which they have from the beginning, making investors to lose in the dumping process that can make the project become useless and having no future. Going for bitcoin is better to avoid scam.