What's the value of being able to verify the beacon chain consensus data?  At it's most basic, if you have a light client that can track the head of the chain, you know the current state of the whole Ethereum world through the "stateroot" contained in the most recent block, which is a 64 hexadecimal string that magically assures that you can verify anything else anybody else tells you about the current state of the world (e.g. what's my wallet's ETH balance? how much USDC does Circle actually have minted, etc)