Metamask is a place to store assets that we have, and can be used to store more than one asset. but to make swap transactions to get a drop, usually it can only be used once. and if you want to get another drop, then you have to use another wallet..
Hey man. You missed up all the criteria of what MetaMask it is. MetaMask is not a wallet! We can say that it's a tool that let you interact with the Ethereum blockchain by using your browser. MyEtherWallet function in the same way but as a web application not as extension. There are several tools/methods to interact with the Blockchain, MetaMask is one of those tools and your wallet is also another tool. But please don't confuse with a client (wallet) and a browser addon.
The concept of "account" , as how you know it, don't fit with the Blockchain protocole .