There will always be divided opinion on this because people are coming at it from very different angles.
One result of this policy is that it encourages couples to perhaps have similarly matched (but not huge) incomes. Eg a couple with good, professional, but not hugely paid jobs, each working a 4 day week and earning 30k, keep their CB. Whereas a couple where one works all hours and earns over 60k lose theirs. Now- I prefer the first model. I think children benefit a lot from having two parents who aren't ridiculously stressed out with having to chase promotions and be the sole earner of the family income. However, if you prefer the traditional model of one earner and one SAHP you're naturally going to be against the idea. I do, however, feel that whatever ones personal views, a model which promotes more of a sense of equality across the genders with regard to earning and parenting, is a better reflection of the 21st century. And please don't anyone misinterpret that as SAHP bashing. As I say, each to their own. But the way the world is now is not necessarily going to reflect ones individual choice