I do get attached to some. But I hatch out babies with the intention to sell them and so I know that they should be leaving soon(after eating and such, of course).
It's like raising animals for food too, that you can raise them and care for them and make sure they're as happy and healthy as possible but you know that they won't be around forever.
But there's always that one that will just somehow be special. Sometimes it's how they look but sometimes it's just them.
I have the same issues with the rats too. I can justify keeping females as future breeders, so I can cheat with them sometimes.