I always like to wipe the machines down before I use them. Then I get the benefit of knowing the machine is clean.
I don't worry so much about wiping them down after I'm finished because my assumption is that the next person only has to worry about me having used the machine before them, and I'm mostly clean (after having just wiped everything down).
If they choose to follow my protocol and wipe the machine down before their use, then they will have an absolutely clean machine, and will have nothing to worry about.
If they don't, then the machine's still only had one user before them.