Washing your car in a driveway or on the street is bad for our environment. What runs off our cars runs down the driveway and goes right into the storm drains and then into the lakes and rivers untreated. The oil and dirt and harsh detergents that runs into the lakes and rivers is toxic to the aquatic life and wreaks other ecosystem havoc.
On the other hand, Federal laws in both the U.S. and Canada requires commercial car wash facilities to drain their wastewater into sewer systems, so it gets treated before it is discharged back into our lakes and rivers.
Think about this the next time you plan to have your car washed.