Why do hard forks happen?

If hard forks can drastically reduce the security of a blockchain, why do they happen at all? The answer is simple: Hard forks are upgrades that are necessary to improve the network as blockchain technology continues to evolve. Several reasons can be behind a hard fork, and not all of them negative:

• Add functionality
• Correct security risks
• Resolve a disagreement within a cryptocurrency’s community
• Reverse transactions on the blockchain

Hard forks can also happen by accident. Often, these incidents are swiftly resolved and those that were no longer in consensus with the main blockchain fall back and adhere to it after realizing what had happened. Similarly, hard forks adding functionalities and upgrading the network usually allow those who fall out of consensus rejoin the main chain.