Because the teams of these projects hold different events to interest investors and raise the price of their coin. That is why the price of their coins after listing does not fall, but begins to grow.
The market moves under the influence of supply and demand. In whatever events the team did not participate, the price will fall if no one wants to buy. I have examples.
In the case of the ROMAD project, the situation with the price of a coin is folded differently, because users will need project coins. This means that there will always be demand for them and the price will not drop very low.