I've been doing OLD for a couple of years, and I think I've only had a couple of unsolicited dick pics (and frankly, the dick pic was better than the saggy grey underpants and beer gut pic that preceded one of those - I did wonder what his thinking was, but better not to engage by asking.) Nearly all matches have offered to send pics, but they do usually ask rather than just send it. But it could well be an age thing - I'm mostly looking at men around age 50, and we didn't grow up with mobiles and the Internet. I don't know. I get plenty of requests for pics, too, and I suppose they're thinking, "I'll show you mine if you show me yours" or more, "I've shown you mine, so you'll feel obliged to reciprocate."
(Not one of them has been called Nigel. Or at least, not one has had a profile name called Nigel.)
In any case, it doesn't matter how many ask, because it is about unsolicited ones, and it only needs just one to be wrong. I assume some get off on the flashing aspect of it, else I don't understand why they do it. However, even if they don't prosecute every offender, they can probably do enough that most men will think it's too great a risk and won't do it. I assume thst is the aim anyway.