It's not as stupid as you think. If you don't know what you are going to do with the data, particularly with low level network packet data like this, it is tricky to sanitize it in a way that it will be useful. That actually requires a ton of thought, and it is way simpler collect the data, keep it isolated, and then come up with ways of accessing/collecting it that protect against privacy violations.

Here's the thing: almost all of the privacy violations that people actually reference in the articles about this issue are data (e-mails, login passwords, URL's, etc.) that are already being transmitted to ISP's (where ironically, there has been a lot of discussion about them being required to archive this data). ISP's have a far less fragmented and transient view of the data than a Google Street Car, and they know precisely where their customers live. The only possible privacy violation here is with data exchanged between systems within the LAN of the home, which is a very different kind of information, is generally not that useful when viewed as a few isolated packets, and which requires a degree of technical sophistication such that you'd really think the same people doing it would also know to encrypt their wireless networks, even if only with something as lame as WEP.