The major benefit of such a card is that it would allow the government to identify people quite easily. There would not be the problem that we have now in which different states use different standards for giving people identification cards and there is no real database for all residents of the country.
There are two potential drawbacks. One is economical. It would cost a lot of money to do this. The other is legal/political. There are many people who would see this as unwarranted government intervention into people's lives. They would fear that these ID cards would be the first step towards a police state.