When you can get out of a pair of jeans and into stockings, suspenders and heels in the seat of your car in about 30 seconds flat (and back into 'normal' clothes even quicker!
Oh and when your car is like a second home with all the shoes, spare clothes, nickers, hold ups, make up bag, jacket and coat (for all weathers) bottles of water, mints, secret (emergency) stash of condoms, wipes tissues....etc etc, All that's missing is the kitchen sink