This has been suggested many times before. I don't agree, because it would lower the cost of CS pets. And there are 3 retired CS pets, Omni, Kioka, and Liyure. Thier eggs are currently worth 45-70mil. If you could breed those, all rarity of the pets would go lower and lower. Same with seasonal pets.
Also, if you look at the "topics not up for debate" thread in this section of the forums, you'll see that this is listed. Basically for the reason Caya stated and it's just not what Res was meant to be.
Normal User
Normal User
Normal User
Normal User