Honestly, it's because I just don't care. I'm not worried about her changing plans or going somewhere without telling me (the feels dirty just thinking about) and at a certain age, I also won't care what my kids do. They will also change plans, or explore off the path. So what? But that one time I _really_ need to call them or they need help, we will be glad they have a little bit of tech on them.
I also find it somewhat interesting that many of the same people who are so worried about this type of surveillance _already_ have the devices and/or technical knowledge to surveil others and choose not to for whatever reason. For example, we have home networks and could track what our families do online. We _could_ put a malicious app into someone's phone, or a tracker on someone's car. Simply having the ability to do something does not imply that it will be done, and certainly doesn't imply that it will be done maliciously.