What are the main pros and cons of implementing protocol changes on Tezos via hard-forking vs onchain-governance?
Here is a link where Arthur B. talks about the need for hard forks:
The summary is that new features should be done via on chain governance as they can be contentious and we want to avoid centralization. On chain governance empowers stakeholders to vote on whether they want those changes. But since blockchains are still software and software may have potential issues that requires hotfixing, hard forks are exercised to avoid crippling of the network.