Because they are specifically promoting porn featuring women as young as legally possible. "Legal teens" would include 19 year olds, and they are trying to create the specific expectation of women who very recently turned 18.
>Why barely, which also means "not really"?
That is not what barely means at all. Barely means "only just". Barely legal means legal, but very close to the cut-off.
Not at all? Well, it is possible my translator (leo) is wrong. I think i have a fairly good understanding of the english language, but i am not a native speaker, so i tried to check my understanding.
I still think it has in this case at least the connotation.
That is the link: http://dict.leo.org/ende/index_en.html#/search=barely&se...
Anyway, if I were learning English I'd pay the $300 for an Oxford English Dictionary. You'll learn a lot that way.
This is a special case. I know that normally barely meanst "only just" (though i believed leo that it sometimes - in special cases when used in a specific way - can mean "only almost"). But if someone hears a sentence like "that is barely visible", one always implies that it is not visible at all for someone seeing a degree worse. Now, if you vist a pornsite with usergenerated content - take 4chan as example - I'd bet a lot of money that one would find a mod-guideline or at least a discussion about such a guideline to delete any threads with "barely legal teens" as topic because a lot of users would post pictures of underage girls in such a thread. In such a case, barely implies not really. And therefore such a term can have another connotation than its formal meaning.
It is really a stretch to say "it doesn't have that connotation", connotations can vary even in one language for every speaker.