[n1c00o]

> But why do these protocols need built-in economics?

I believe, in this time of humanity where economy matters, that Blockchains have built-in economics for two reasons:

1. They all started copying Bitcoin, which by nature is an economic system (this is the goal of the Bitcoin's paper). 2. Reward by money is a common way to attract a sustainable amount of active users that keep the network alive without evil intention appart from making "quick bucks". In contract to volunteer networks such as Tor, where a lot (even a majority) of nodes are run by gov. agencies with the goal of identifying users, popular blockchains are still run properly since users are focusing on money and not destroying the network.