It is relevant because if something has a use, there is a basis for the value. If something is only valuable because people believe it to be valuable, then you

It is relevant because if something has a use, there is a basis for the value. If something is only valuable because people believe it to be valuable, then you must maintain that belief in order to maintain that value. For instance a used stamp that is rare is valuable to collectors even though it has no use, but aside from a few collectors there is no market for that stamp. The problem with a huge market filled by people buying due to speculation is that as soon as something spooks the market it tanks and the value doesn't hold, because people don't actually want the thing they are holding, they just want to be able to sell it to someone else. This is why the crypto scene is very cultish -- it is all built on maintaining the belief, and the utility is secondary.