But we have a very unrealistic view of what's harmful to children. Non-sexual nudity is not a threat, period. Playboy--yeah, because of some of the tobacco ads clearly aimed at teenagers. The nudity--harmless.
I grew up in a household where no effort was made to hide adult materials. Oh, the horrors--that don't actually exist. There is exactly zero overlap between my father's kinks (I was the one that had to go through his stuff when he died, I know what they are) and my own.
As for the billboard--there's sometimes been a prostitute ad on a billboard here. "Full" nudity with strategically placed text. Of course it pretends they are dancers but few people are actually mislead. (Despite a fair amount of misunderstanding prostitution is *not* legal in Las Vegas. It's banned by state law in the two most populous counties, local choice otherwise. However, there's pretty much a truce between the outcall escorts and the police--they don't do other wrongs, the cops don't try to catch them.)
Most adults would be put off by that as well, I’m not sure if this is indicative of public spaces.
That said, I agree that public spaces cannot possibly be adult only by default, as children have to traverse them.