Not everyone is educated.
Look at those scammers and thieves who are on always on a prowl for unsecured sites, they do it because there is no central entity that will fuck him up if he did those things.
So, we sometimes need it.
Yes of course, the idea of decentralize everything is good but the process might be very very difficult because some people dont like to "decentralize" all the life aspect (yes I know it is hard to understand, but this is true). The freedom and the decentralization are really correlated.
some people don't like decentralization, because it take away the security, you need always to trust a third party with decentralized system, that's the only problem i can see, otherwise decentralization is the future
Yes of course but if you know that "part" is honest because is governed by a code and you know this code because it is open source you should not have to worry. The hack of those various exchange aren't related with the bitcoin code itself, isn't it? However I agree with you, the future is not more centalized .
Fiat isn't really "code" though. Even when digitized, it's an entry in a centralized database. I don't think the problem of exchanging fiat to BTC and vice versa will ever be solved in a decentralized and trustless manner for various reasons. Ripple's distributed ledger model is probably the closest thing to a decentralized fiat-BTC exchange that we can achieve right now and even so, it's not actually decentralized but instead distributed and you still need to trust the gateway that converts the IOUs into actual funds:
http://ripplefederation.org/forum/why-must-end-users-be-forced-to-trust-gateways