PayPal demonstrated how fines/deductions will work for 'misinformation' (anything the government disagrees with).
Bank of America demonstrated how certain purchases will be 'declined' (guns for example).
Canada demonstrated how accounts can be locked or even confiscated if the government disagrees with your political views.
A government controlled digital currency essentially puts the government as the 'primary control' on every account in the country. Government becomes a parent over your money, controlling how much you make, how much you allowed to keep, and what you are allowed and not allowed to purchase.
Also, they will have detailed knowledge, an inventory of everything everyone owns, down to the number of cans of soup in your cupboard. This would be a dream come true for fascist authoritarian Democrats. Which is why they want it so badly.