Why don't we breathe nitrogen when it makes up most of the air?
Animals use oxygen as a chemical energy source because oxygen gas can react with many other compounds to form oxides, which releases energy and happen spontaneously.  

Both carbon and nitrogen can be made to react with oxygen, but otherwise they are pretty inert.  So of all the gasses in the air present at over a fraction of a percent, oxygen is the only one we can use for energy.

Hydrogen (and sulfer) are both possible substitutes for oxygen in the role of redox energy source, but are normally pretty small components of our environment.  On another planet they might well be the basis of biometabolism.

Of course the fact that plants can use carbon dioxide to fix carbon is a different case of biology using a gas out of the air.  Its the defining quality of plants!   

The energetics of using CO2 is endothermic - it requires energy input. They have to use sunlight to get the energy to utilize this energy and its very costly energetically.  Animals can afford to move and grow because they use oxygen while they eat plants.