A couple of points:

One is that common sense isn't something that everyone has about everything. Believe it or not, many people either don't know that they shouldn't be giving out certain information. To give you an example: I work in a place that requires us to hold onto a customer's photo identification. Sometimes people don't have any on them, so they try to use their credit card. They simply don't realize that most credit cards include enough information on them to conduct fraudulent transactions.

The second point kinda ties into the first. Even a person who is quite dilligent about not handing over personal information may be unaware that they are inadvertently handing over personal information when using certain software or online services. A phone's a phone. A game's a game. Why should playing a game on your phone tell the game publisher where you live? It may not do so directly, but they can certainly infer where you live based upon your geolocation data. In many cases they can make a good guess as to who you are based upon cross referencing with other databases (e.g. phone directories). Get the right types of data, and you can actually tell a fair bit about a person.

So no, it's not a matter of common sense.