this may due to two reasons:
The first reason is that the coin or token has no real value.
The second reason is the large sale of those who got his coin free such as airdrop.
Isn't that true?
I'm not sure we always see an initial price rise. The coins I've followed, they always drop straight away as soon as they are tradeable. Part of it is ICO buyers who received a big bonus cashing out, and part is bounty hunters selling as well. Fundamentally however I think its a question of supply and demand. If the coin doesn't hit hardcap at ICO, then supply is more than demand, and this creates downwards price pressure - there are simply more sellers than buyers.