Yet, those examples are useful because they prevent people dismissing the arguments because `people shouldn't be doing that anyway`. That is, no-one wants to keep people from going to cancer-related websites. This is very different from e.g. porn or STDs. I guess perhaps the exception are the nut-cases that believe people getting cancer `deserve it` because otherwise it wouldn't be part of gods plan. But luckily very few people consider those opinions relevant.
Apple's contrived example from when they introduced private mode in Safari was shopping for presents and not wanting the recipient to find out, but that would be even less convincing when the person you're hiding your traffic from is the person next to you in the coffee shop.
So, yeah, I'd agree it seemed both jarring and unnecessary.