Based on your profile, it looks like you've been a member for only a couple of weeks. It's pretty early to expect much (anything) in terms of earnings. People do make money, although the kind of Hub you write makes a big difference. If you write about something people are searching for, and your Hub is useful and unique you're more likely to earn more than if you write for the sake of writing (without paying much attention to whether people will be searching for the subject). Then again, with lower-earning kinds of writing you can make up for it some with lots of Hubs. If you don't write Hubs just for the purpose of earning, and want to write "what you feel like writing", you can always boost your earnings by writing what you like (for the most part), but throw in a few "higher-earning type" Hubs into the mix.
It also helps to come up with titles and key words that will increase your Hubs' chances of getting traffic.