BTC - store of value
ETH - actual use cases (stable coins)
Hive - still waiting for some proper economy to grow that could create sustainable demand - in my opinion that could be:

• blogging obviously - users may want to support their favorite authors, more stake in the platform
• gaming - hive as the currency used by different games
• ads - things like allowing authors to promote their content should be build in since day one
• financing - lending (delegations also), stable coins etc.

Obviously, the more uses cases for the currency, they healthier the economy and the more valuable the token. I think we're slowly getting there :)