Not caring about digital privacy can stem from being overwhelmed and defeated. Everything we use is tracking us and selling our data. It used to be just websites, but now even dishwashers need to be connected to the internet.
It's not always obvious how to establish privacy either. Like, your web browser just needs an extension, but how do you block trackers on your tv?
If you attempt to block everything but reach a thing that you can't, it feels like it ruins the whole endeavor. Like, you can stop your phone from tracking your location, but your car will still be able to. So now your location data is out there anyway. It's inevitable, yay.
It's not just companies either, governments also heavily tracks us and will cooperate with each other on it. For example, if we assume that the US is being honest about not spying on us, it still doesn't stop them from buying our info from China or Britain.
Establishing internet privacy is simply too hurclean of a task for most people to handle. It takes a lot of time, education, and stress to do, and likely won't be enough.
Worst of all, if you somehow manage to create complete privacy, you won't have anything to show for it. The benefits are too abstract. Internet privacy or not, you still need to find a job, go grocery shopping, etc etc. None of which are noticeably impacted by data privacy.
It's much much easier to just not think about it.
In addition to what others have said, this paper serves to directly address a very common talking point.