>>2185436I've thought about this a lot, being an inveterate armpitfag.
The most obvious factor is it's a highly gendered part of the body, and I don't just mean because women remove the hair there. There is also a bit of breast and fat tissue distributed under the area of the chest bordering the axilla, so even the girliest-looking trap is basically always given away by an armpit shot. This might sound like a fucking stupid virgin factoid, but it's a well documented anatomical feature called the tail of Spence. Google away.
Poses exposing the armpit also tend to give a good view of sideboob, but even if they don't, I agree with this anon.
>>2187644 
