Leather waterproofing products are oil based and use various complex combinations of oils, waxes and sealants to plug up the leather pores thereby creating a barrier to any liquid.
Care should be used before waterproofing any indoor furniture that may be subjected to cat or dog urine. If you favorite pet decides to use your expensive leather furniture as their personal toilet how will you clean up their urine when your waterproofing product has plugged up the pores?