In the customers mind if they see a machine it's a professional job, no machine it must be a con, it's as simple as that ! Most are not interested or even want to understand how you clean the leather or what knowledge you have, they draw a conclusion from what tools & setup you use.
I've often had carpet cleaning customers say the last guy just used a buffer to clean them, he probably did a fairly decent job but in their mind it was inferior because they perceived he was using a buffer !
You have to see things from the customers viewpoint & dramatise it a bit so they feel they getting value for money !
Steve