You're throwing money away on your utility bills
The Department of Energy estimates that 30% of your heating and cooling costs are due to air leakage. That means that 30% of your bill is used on air that isn't going to heat or cool you or your home. A separate study concluded that because of incorrectly sized or incorrectly installed HVAC units 3/4 of homes are paying an additional 25-50% extra. Combine those, and that is a lot of money you are spending.
But you don't have to be.