I am very curious... if husband earn more than wife, should he contribute more money to the family?

I would say yes. Same to the logic if the wife earns more, the wife should contribute more. Contribute meaning that pay more for the grocery etc. however, there is no need to draw an obvious line or do any recording of transactions. So long both knows who has been paying more. But the lower income spouse can always initiate the spending as well. My stand would be yes. I don't think union is based on financial needs in this case. Because as much as you love your spouse and knowing he/she earns lesser, you would want to give more so he/she can have some spare for himself or herself in times of needs.