Still with any individual currency there is a market where mandated by law you can pay in this currency, or where you can pay taxes in that currency. So zheir value has a real and a speculative part. Crypto only has a speculative part and that part is often and strongly influenced by deliberate manipulation.

And if yet another crypto currencies is pushed it is highly questionable if there is a serious intent to deliver on the promises made to its laternuse or how much is just scamming people into an ICO and then running with that money.

Look at piracy, torrenting, usenet, etc. So long as people can make encrypted connections, crypto will continue.

Do you mean cryptography in general or cryptocurrencies in particular? Because cryptocurrencies ultimately do need an interface with other currencies, or some economy, where you can pay with them. If you cannot buy any real product or service with it, it has no value. Lets take Darknet market drug dealers for instance. They are not selling drugs because they like bitcoins and buy other drugs for themselves with it. They are selling drugs and exchanging the bitcoin into some fiat currency, so they can buy normal stuff with it.