I can only assume you've never ridden a bike. You sit down on the saddle, it's not as if male cyclists are waving their genitalia around.
As others have said, it is to raise awareness of vulnerable road users - 1633 people were killed on the roads in 2024. I'd be more concerned about that than the potential of seeing a penis, given that you'd have to (a) be on the route, (b) looking directly at their crotch region as they cycle past, and (c) looking sufficiently carefully to see their penis given the folded up nature of cyclists in that area.
Honestly, this says more about you than any cyclists, or men.