That is true in a legal sense. That's why I put "legally" at the beginning.

The point is there are no legal hurdles to overcome for the government. These are the most difficult and this is absolutely true. Legally we have very little if any privacy in public. The only hurdles are technological ones, which automate the inspection of people in public areas. (i.e. facial recognition cameras).

Police can spy on your in your own home legally, if you leave a window open, because you just made that part of your home public. They'll setup across your yard and watch you with telescopic lenses. Police also spy on people in their own homes using IR and thermal cameras, which cannot be defeated easily, and this crosses (leaps) the boundary of your home being private. Apparently the thermal radiation emitted is now public space. I remember this in court, but don't remember the outcome.

I suspect though that when these laws were made, lawmakers didn't anticipate the ease and scope of which automation could make spying. Maybe they'll reconsider, but the police departments have a lot of sway over lawmakers, so I seriously doubt it.

Have no doubt though, police aren't interested in your privacy, they are interested in arrest counts. Privacy laws are an inconvenient burden to their jobs and they will use any methods they can think of to circumvent your privacy rights and argue technicalities in court. They will usually win.

Of course, all of this was enabled with the War on Drugs.