To be honest, I am also still in the learning phase of all decentralized Crypto-based financial systems.
However, from what I know, maybe the reasons below can help you.
My opinion on Decentralization Applications is of course related to security.
We take the example around 2016, One of the market market cryptocurrency without decentralization such as Coiffeine and EtherEx are experiencing problems where the risk is borne by the user if it turns out to be a fraud or a hacker attack.
But with these decentralized apps, users can reduce fraud to "zero". All Bitcoin exchange transactions and other cryptocurrencies can also run directly.
May be useful.
READ ALSO My Other POST: 8 Reasons Why BITCOIN is better than the Bank?
https://steemit.com/cryto/@yd9rsg/8-reasons-why-bitcoin-is-better-than-the-bank
RE: 3 Promising Types of Cryptocurrencies