You didn't get paid for looking after your own children - neither did I. But both my husband and I paid tax and NI as well as looking after them when they weren't at school, as most parents do.
I don't want to make this personal, but I see no reason why people can just say 'I'm not going to bother paying tax, but I still want to use the NHS, educate my kids, use the roads, be protected by the police, and all the other things that tax is paid for' (and yes, I know you will question that), and then say 'Oh, you have more money than I do because you and your husband both work. You should pay more because you work, and because I don't I should be able to get credits or other means tested benefits'.
I'm not saying that tax shouldn't increase the more you earn - in fact I think it should be higher than it is now, so that it can pay for more universal benefits and services. But I also think that all adults who are able to work should do so, and the working partner's taxes cover them, based on their income. They don't cover the other one.
Also (you did ask
) the working couple are paying two lots of commute charges, for two lots of work clothes, lunches etc, and in many cases very high costs for childcare, which are not paid out by the single-earner couples. They are the tax breaks I mean. Oh, and NI contributions are paid for the non-working partner too.