I was also confused.

I would start with this: https://steemit.com/steem/@steemrollin/steem-where-does-the-money-come-from

and then https://bitcoin.stackexchange.com/questions/182/where-do-bitcoins-come-from-and-what-gives-them-their-value

and finally a Tim Ferriss podcast is a MUST listen. He basically asks the same question like you did.

http://tim.blog/2017/06/04/nick-szabo/