That's because of economies of scale. It's much cheaper/easier to do something when it's the only thing you do. It's why we have professions, rather than each of us doing a bit of everything.

i think this is mostly because of the maturity/popularity of the tooling, not the underlying aspect of centralization. if there was a just as slick, widespread and useful decentralized alternative, i would be on that instead.

Depends on what problem the adoption of decentralisation is solving. There's no point choosing a decentralised option just for the sake of it.

i think i would choose decentralized almost all of the time if it worked the same performance wise