I'm not at all used to hearing the word cock or dick, and when I do hear it it's mostly in very inappropriate ways that are intended to make the listener uncomfortable. If it's only been used crudely around you, you think of it as crude. I think if you've built a comfort level with your lover around the word than it can be completely appropriate and sexy, but it's harder for a writer to build that comfort level with us in their story - they're trying not to scare off the people who only see cock as a violent way of talking about the penis, rather than a romantic way.
Personally, I think the easiest way to build a comfort level with us, the readers, is to simply use penis in the description, and let the characters say whatever is IC for them (whether that's saying 'I love your dick' or not). We suspend our comfort level for the character's communication, but not the writer's - usually. Am I making any sense?

Yes, hard member is just bad. Making it too abstract takes away the intimacy of the writing and ruins your intent when it comes to conveying the smut.