> You aren't trusting an exchange when you send a transaction on the blockchain.

This is true, but exchanges have become the de facto on/off ramp for cryptos. If I want to acquire bitcoin without mining, how am I going to do it other than buying from a centralized entity?

Edit: As I post this I remembered that Paradex, a decentralized exchange for ERC20 tokens built on 0x, was recently acquired by Coinbase[1], the largest centralized crypto exchange, who in turn might soon be acquired by Facebook[2]

1. https://www.reuters.com/article/crypto-currencies-coinbase/c... 2. https://www.independent.co.uk/life-style/gadgets-and-tech/ne...