I'm inclined to believe that DC is saying no, more than creators not asking at all. As Godlike said, Dick was supposed to be a big part of No Justice, but somewhere between concept and final product, that got changed. Bendis wanted to use Dick in Event Leviathan and couldn't. And I want to say that Snyder has said Dick is one of his favorite characters, but got a bigger fish with Batman.

It's also true that Dick is a whole lot like Batman, only without as much angst and brooding and inner conflict....but that's entirely on how DC has allowed him to be used since Dick returned from the Titans office. At one point Dick was like a Bat living in a Super world and he wasn't just doing standard street vigilante stuff. But DC seems to still be intent on downplaying that element of Dick's character, even though a powerless vigilante going up against big superhuman threats is a fairly unique niche that, as far as I know, no one else in DC is really filling.

I also dont think the "too much like Batman" thing really justifies the extent of what we've seen the last few years. If writers didn't want to write Nightwing because he's so much like Batman, then why do they want to write Arrow? There's a lot of characters in DC that overlap each other a lot, I don't think the similarities between Dick and Bruce are that different.