They don't need to make a profit or even enough money to pay the staff. However that doesn't mean that they don't make profit and lots of it too. A lot of these types of businesses are money laundering fronts for drugs or other dodgy dealings.
After all, how does the government/coucil etc know if they cleaned 1 or 100 cars today? The fact that they are cleaning the money means the business has a significant throughput of money and pays taxes, albeit limited by using multiple sites and clever accountants.
Last time I paid proper money, it was £50 for a full valet. Came to my house with his own water and electric. He proceeded to wet clean all the seats and carpets and spent ages gettting the oil out of the boot carpet
. Washed and waxed the outside, the full works. I was very impressed.