Finances is definitely one of the big topics that a couple should discuss before they get married. I have read a lot of stories of couples divorcing because of it. They need to agree on a setup that works for them. The setup of my parents is something that I think works. They each get an 'allowance' that goes to their personal bank accounts, and the rest are put in a joint account. The joint account is used for all the house related needs; food, mortgage, repairs, etc. They are free to do or buy with their allowances. So if they want a costly item, they have to save up for it.
That is a good setup for some I think. I reckon my wife and I should formalize ours more, rather than just going with the flow. I am worse with money than my wife, but due to knowing this, I am also more structured in my spending.