I remember asking this years ago on r***** but I'll ask again because I think this is a fun topic. Every sport has them - what are the unwritten rules of pro cycling?

Any answer would be great, but I also want to ask about something I just saw. Is there a rule among cyclists about intermediate sprints that you can try for points, but not very hard? I see mid-range pushing at these things and I always wonder why at least one rider doesn't just go all out to get the points.