It's uncommon because males need two ino genes and femsles only need one, and for some reason two ino genes makes a bird that isn't as healthy and strong as one ino gene. Theoretically it would be easy to develop a pure breeding line of albino or lutinos just like opalines (both are sex linked recessive traits). All you would need to do is breed ino females with males that carried ino and then breed the ino male offspring to another ino female. Then all babies would be ino. But it hasn't worked out like that in practice. If it could be done successfully breeders would have done it because ino birds are so desirable. I read that inos can have very poor eyesight when they have two ino genes. Maybe other genetic problems, too.
Opaline males are half as common as opaline females. Males need two opaline genes and can be bred with opaline females with one gene with strong healthy all opaline babies, no problems, so opaline males are much more common than ino males.