Distractions at the market

Whilst at work today I saw a particularly interesting pair of girls, presumably sisters (possibly adopted?), aged about 5 and 7. A little under my usual AoA but still rather cute. The entire time I saw them, they were in physical contact with each other in some way. Sometimes it just looked like hugging but other times they were touching in some rather... *ahem* interesting positions. I do not make any assumptions as to their motivation for this highly physical (and public) play, but they sure seemed to be smiling and having a good time. And I could hardly keep my attention focused on my current task as these two were far more enticing to watch than anything I've seen in a long time.

Now I find this unusual because Americans in general, not just kids, seem to have less public physical interaction. Just seems to be the culture. I don't think physical interaction of this nature is inherently healthy or unhealthy. It's kids and they play to learn. While at first I thought "gee I'm surprised their mom isn't bothered by this" but then I realized "I don't think I'd do anything to restrict my kids' play unless it was overtly dangerous".

I dunno what do you think? Is this sort of behavior common or rare? Is it generally discouraged or permitted?