You can't earn free bitcoin. You can receive them for signature campaigns in exchange for regular, quality posts. You could trade them for altcoins, and sell them at their highs. You could provide digital services and request to be paid in bitcoin.
Even solving captcha takes your time so I agree, no bitcoins are absolutely free. Also the faucets give you so little that it's waste of your time mostly. In theory we all know how to earn with trading, but in practice we never know whether an altcoin will go up or down after we buy it.