Steam is good... but the chemicals smell better
When I bought my car there was a stain on the driver's seat (spilt coffee, meatpie...who knows?) The salesman, honest and trustworthy soul, like all car/realestate salespeople, told me that the detailers at the yard tried everything to remove it with no luck. I got it home and tried some 5 Star interior cleaner from Crazy Clarks, The Warehouse or wherever, and to my utter lack of amazement, it came right out with a little spray and some rubbing with a microfibre towel!!!
I bought this amazing product called seatcovers that will prevent me from a repeat of the stain (it is my constitutional right to drink coffee and eat pies in my car while I am driving!) The covers are great as they have the same mesh appearance as the original seats as well as being side airbag compliant.
The covers I had in my Camry kept the seat in original condition that I was amazed when I took them off to sell the car.
Scotchguard would probably be good if you have any of those small dirt and stain creating creatures that people often have in the back of their cars :P