To be honest, there are only a few of them with an actual use case, the majority are either shitcoins, pump and dump or coins of zero use/value, the thing is, many of such coins still manage to garner interests from some investors because many of them are only looking for short term profits, and pump and dump coins are good for such purposes, but come with a high level of risks. Having said that, amongst the many coins in the network, Bitcoin and ethereum prolly looks like the only ones that can be said to be sustainable for the long term cause of the demand/use of them.