Because you want to buy a house? If you are borrowing 8k for a simple car @2%, 5 years, you are repaying ~140/month. On a 20 year loan @2%, that same monthly payment would net you 30k.
My native country has a central database of every single loan outstanding. Lenders have to consult that before granting a loan and stay within certain limits. So at least here, an outstanding car loan might disqualify you from a home loan because of a lack of solvability...
A five year new car loan from a credit union -- no shopping around -- has a cost of something like $58 / $1000 borrowed. So even if you have $20k cash on hand to buy a new car, for a thousand bucks you can maintain an extra $20k of liquidity for expenses that are more annoying or more expensive to finance, like auto repairs.