Why Decentralization Matters?

I keep reading about the decentralized internet, internet monopolies, data privacy, ability to control the protocol, the network and that the pioners of the internet had a different vision.

I feel that it's an important topic to explore and have a thought process around it.

But, I am missing the key building blocks for the idea and I am not able to build a narrative about the importance of decentralization or do we really need it?

I want to understand the topic from the first principles and the conflicting philosopihes around it.