Respuesta :
Because we have a large selections of jobs ranging from plumbing, carpentry, etc... So we have the ability to chose something that we as individuals are good at!
We live in a society based on a division of labor. It is very inefficient for everyone to do everything needed to survive. Instead, we all focus on things we are interested in and are good at and use these specialties to make money to purchase the other things we need to live.