I see that I can login to my MEW using meta mask. But how does that make any sense? I can do all the functions of MEW in meta mask add-on. Am I missing something here?
You can't do all the functionality. MEW allows you to interact with a contract by entering its ABI and address and calling functions. Metamask doesn't do this directly, it depends on websites (dapps) using the injected Web3 to create these interactions with contracts. MEW is one of the dapps that does this for Metamask.