Ethereum is the clearest when it comes to why it's price keeps going up.
Why? Ethereum allows you to create tokens/smart contract on its Blockchain.
So many companies have been creating businesses and apps that make use of tokens in their product and then pre-selling these tokens to raise money calling them ICO’s (initial coin offering). When you buy these tokens it costs Ethereum to create them and it costs Ethereum to send them to others (so the greater the demand for these ICOs the greater the demand for Ethereum)
What we know as Ethereum (ETH) is actually a fork of the original Ethereum Classic (ETC). (There was a large scam ICO on the original Blockchain, a fork was created to reverse the scam and get people back their money).
Tokens that are created on the newer Ethereum Blockchain are called ERC20 tokens which consists of most ICOs (BAT, Augur Rep, Civic, etc.)
There are many other token platforms that exist and many in the works. All it takes is a few successful coin issuances to drive demand for the platforms currency. Examples of these are NXT, Waves, ARDR, NEO, Bitshares, and many more (Waves/NXT/ARDR have built in exchanges in their Blockchain).
Bitshares - Allows you to create collateralized assets that track the value of real things, one BYS asset is called a HERO which tracks the value of a 1913 dollar!
NEO - has a second currency called GAS that is a reward for owning NEO, so it essentially pays you a dividend for owning it.