Because your statement makes no point unless it is a defense of current technology.
Most people don't expect others to look away while you pick your nose at the grocery store. The statement about defending privacy in public is almost always about tracking and the ease of it.
That wasn't the statement I was replying to, though?
Please re-read the thread, without injecting your own pre-conceived notions into it? The statement was simply this:
"Because my business is my business and nobody else's. Full stop."
When it comes to being in public or at a grocery store, this is simply untrue. Being in public involves interacting with other people, at which point it inherently ceases to be just your business, and starts to be others', too.
That entitles them to some amount of say in it, however small it might be, depending on the context.
No where did I say anything about the degree of surveillance?