In this context, it's hard to say why it isn't treated in the same way. Yet I do suppose that it's possible to make several arguments. One is that certain terms of service were agreed to, and the user forfeited their rights in the process. A second one that Internet service goes beyond the scope of your house, so this data is available to certain parties anyhow (most notably your ISP).

As many people have mentioned a multitude of times and in numerous places: there is precious little we can do about it now though. The decision to make the Internet a free-for-all was made long ago, when people demanded that the medium go unregulated. Alas, a lack of regulation means that certain technologies and attitudes were developed that are going to be difficult to reign back in.