We don't owe every single message an answer. We have real lives and our own personal preferences about who we choose to talk to.
I prefer to get to know people out here before moving to inbox in order to keep the creeps out. So I won't and don't open every message I get - and less so when the intro implies any reference to dick or even a dick pic.
@Funlov Most folk don't like it - but I was here in the time before inbox pics were automatically blurred... and I got my fair share of dicks of the literal and metaphorical variety.