Though they have been used for a long time, there are a number of issues.
Security. If someone has access to the server with the information, any data can be added, changed, and removed.
Reliability. If there are a number of requests, the server can break down and no longer respond.
Accessibility. If the central storage has problems, you will not be able to get your information unless the problems are solved. In addition, different users have different needs, but the processes are uniformed and can be inconvenient for the clients.
Data transfer rates. If the nodes are located in different countries or continents, the connection with the server may become a problem.
Scalability. The centralized networks are hard to scale since the capacity of the server is limited, and the traffic cannot be infinite.
Decentralized and distributed databases can solve these problems.