The biggest advantage Bitcoin has from being decentralized is that no central authority can monitor your funds and its transactions. You and only you can control and regulate the flow of your funds.
In a centralized system, the head authority decides the value but Bitcoin is decentralized so there is no central authority therfore the Bitcoin network decides the value of Bitcoin. The more popular the Bitcoin gets, the stronger the network will become, the higher the value of Bitcoin will become. Decentralization is one of the main reasons why Bitcoin has so much potential to grow.