Is KYC mandatory for all?

Is KYC, or Know Your Customer, mandatory for all cryptocurrency transactions and platforms? The topic of KYC has been a contentious one in the cryptocurrency community, with some arguing that it's a necessary step to prevent money laundering and terrorist financing, while others believe it infringes on user privacy and goes against the decentralized nature of cryptocurrencies. So, is KYC a blanket requirement, or does it depend on the specific platform or transaction?