The advantage of decentralization is that no one can touch assets: a decentralized currency cannot be changed, manipulated. And in this case, those who are accustomed to currencies such as dollars or euros may find it difficult to understand this advantage. But those who are used to manipulating currencies (for example, Venezuelan Bolivar) or strong inflation (for example, the Argentine peso or the Turkish lira), they know exactly how useful decentralization can be. Sooner or later, any fiat coin may suffer from manipulation or excessive inflation. Then the concept of decentralization will be a big advantage.
The other advantage is tracking
The fact that all transactions made with the wallet are unchanged means that there will never be a dispute about making payments. These programs are visible to everyone and can be shown at any time.
For example, even if different individual addresses are used to receive or send tokens to other recipients, the whole story is available. Also, since transactions are public, not only the sender, but the recipient can see the whole story (which is beyond doubt).
The main advantage is the deflationary nature of many decentralized cryptocurrencies.
Since there is a limited number of GDAX cryptocurrencies available. This means that they are immune to inflation caused by the release of excess money. Consequently, the price of cryptocurrencies increases over time. In other words, they can also be a good investment, even if nothing and no one can guarantee that you will make a profit by investing in this way.
These are the advantages of using cryptocurrencies instead of fiat. Others will likely be added in the future, as the technology will evolve continuously. The advent of protocols such as the Lightning Network also increases the potential for innovation.