They clean up just fine w/o it. The cutting board I use the most is bamboo. That one has never been oiled.
My wooden one hasn't been oiled in years. After using it, I wash it with hot soapy water and let it dry. If I think it needs it, I rinse it with boiling water.
I'm reading that, if you don't oil them, they'll dry out and crack. Mine haven't.
My biggest cutting board is over 20 years old. But maybe I'll oil them this week.