I picked up my rare Crow as a secondary to a rare Glowfly! So I picked to Crow to capture... it took me much longer to then find a rare Darkmoon Glowfly again, but eventually found a rare secondary to a green one.
There's another way to look at this. They could well be leaving them there because they know there's still a lot of other people wanting to capture the glowfly. It's not all about people who want Crows.