"I'm in public" is usually a lie
Seriously, are you guys actually buying this? If you're in public and you're with people, you probably aren't getting deeply involved in a conversation over text message in the first place. Yeah, sometimes it happens, but if it happens twice or more in a row where the girl claims she's out so she can't be bothered to send you a nude, it's a lie. Who knows? Maybe she really is out that often, but she could easily send you a recycled nude or a fake one. But she's not. Maybe she's not interested and is breadcrumbing you because she's bored and wants attention. Or maybe she's actually totally about it, but she doesn't want to give you the wrong idea that she's easy.
[Photo via @letthelordbewithyou]