Indeed, when we give token to the exchange, it is only based on trust.
A number of exchanges have been stolen recently, and some centralised exchanges may be able to pay for some of the stolen tokens, but the decentralised exchange...
Bitcoin can be anonymized, which will allow everyone freedom to talk about economic value, free from snooping by criminals and by unequal laws of corrupt governments. Of course, bitcoin anonymity also brings disadvantages, such as trading platform needs to verify identity. Some platforms have purchase limits each month, or more personal information is needed to allow for more purchases.