The definition of a leather cleaner is a cleaning product that is water based and contains no oils, waxes, sealants or polyurethanes that can clog the pores. Cleaning of the leather surface is what they are designed to do without leaving any type of residue behind that will complicate your cleaning in the future.
Specialized leather urine removal products go even farther by penetrating the leather to remove embedded urine that has seeped into the cushions and padding.
You bath in water to remove the dirt and body odors. Would you bath in a bathtub full of oil? Probably not but we hope this example has cleared up any confusion you had.