They are tired of their kids and don't want them around any longer. Unmasking them and throwing them in with tons of others could quite possible get them sick and die or cause others to get sick and die.
You say that is ridiculous? Since when is PROTECTING the life of your child a bad thing? Since when is exposing them to possible illness and death preferable? What a crock of bullpuckey!
Arizona parents. Too bad they weren't sterile. Of course they could have adopted and done the same thing. Bottom line. Kids are hostages of their parents and victims of parental stupidity.