As a plus, Google+ integration into other services sees Google collecting data such as comments and your approval of various items through giving them a "+1". Such data can be used by Google to improve its products and to understand its users better.
As for Google Reader, Google is clearly not interested in the service, and doesn't see much value in it. With "few" users, there probably isn't much value in mining Reader subscription data.
It is therefore both in Google's best interest and that of Google Reader users to drop the product. Being the most popular feed subscription tool, it's demise gives an opportunity for a new, focused player to emerge and built on a better product. A focused player is also has a better chance at finding a way to make value off a feed subscription tool than Google has.
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