Because in case you haven't heard - or rather, seen their little pop up notice - Google's shutting down the RSS reader in July. They claim that it's because the number of people using Reader is "declining" and that they're trying to reduce the overall number of products they have. Dumb reasons, if you ask me. If Reader was in decline, then why not simply redesign it to make it more attractive to both old and new users and give it just a tenth of the promotion that Google Plus, Chrome, and other products receive? As for the latter; nobody told Google to go and create twenty million things that no one was going to use.
Pulling the plug on something that a lot of people still use just because it isn't as popular as it used to be is just ridiculous. If other companies followed that line of thought, then no one would have a landline, because AT&T and the other phone companies would ditch it because of "declining use".
It also makes me question the value of using any of Google's other products, like Plus and their Play store. Are those going to go the way of Reader if they decline too? They're not giving both current and potential new users much incentive.
Anyway, if you're looking for a replace, CNET has a list of five free ones. I'm trying out Feedly and it looks nice and you don't even have to register an account to use it. Unfortunately, it's being swamped because of the announcement and CNET's article, so patience is a virtue.