"Aerobic endurance training results in reduced body fat, increased maximal oxygen uptake, increased respiratory capacity, lower blood lactate concentrations, increased mitochondrial and capillary densities, and improved enzyme activity."
"Physiological adaptations to aerobic endurance training:
-Respiratory system:
*Enhanced oxygen exchange in the lungs
*Improved blood flow throughout the lungs
*decreased submaximal respiratory rate
*decreased submaximal pulmonary ventilation
-Cardiovascular system
*Increased cardiac output
*Increased blood volume, red blood cell number, and hemoglobin concentration
*Enhanced blood flow to skeletal muscle
*Reduced submaximal heart rate
*Improved thermoregulation
-Musculoskeletal system:
*Increased mitochondrial size and density
*Increased oxidative enzyme concentrations
*Increased myoglobin concentration
*Increased capillarization in muscle bed
*Increased ateriovenous oxygen difference"
-Essentials of Strength and Conditioning, 2nd edition.
There was also a study done, which that book talked about which displayed all of these facts.
If these are adaptations that you don't feel will make you healthier, then by all means, don't do any "aerobic" work...