I thought the same as you- plain water and a thorough rinsing is just fine, then ass deodorizer for the scent afterwards. WRONG! My sales lady from Jon-Don (Linda) asked me to try a free sample she sent me of their rinse. OMG- BIG DIFFERENCE! Not only did it already have the smell customers expected from a cleaning, the carpeting was much softer and it got lots more of the prespray out (I checked with my ph meter). Yes, it is a little more money to put into each job, but well worth it. (I am the tightest ever with my few dollars but can't work without it now.) There are many rinses out there, just check them out and settle on the one best for you.