Supply and Demand.

If there's somebody who want to buy the token for whatever reason, it will have a value. Just imagine that these coins that you are seeing right now are like Bitcoin when it was starting way back in 2008. Yes, it already has a use case at that time (base on the wallpaper), but nobody really cares at that time. Nowadays, people will invest into different coins for different reasons.

Whether it's profit, or the technology behind it or the use-case. However, many are still investing into coins that has no real use-case at all because of the fact that they believe that they can earn money when they invest on it.