"People will work because they need money to live." Though I do believe that there are a lot of other reasons for people to work. I will enumerate each of these reasons in the following paragraphs.
According to me, all of us have an inbuilt burning desire to SUCCEED. Success is a combination of professional achievements and then earning money as a result of these. Even if one of these components is missing, one will not derive true pleasure of having succeeded. Thus it is a big chain of events, one enjoys one's work, and the moment one's work is not to complete a job but an enjoyment, and one works even harder. More hard work over the long run inevitably leads to professional excellence which in turn translates in monetary benefits.
Secondly, when a person works hard, he contributes directly or indirectly to society. This feeling that "I have some worth and am contributing to betterment of society" is very important for mental happiness. Being an orthopedic surgeon myself, I have experienced this numerous times. If a patient comes to me with a fracture and then goes home walking, the pleasure I derive is phenomenal even if I don’t derive substantial monetary benefit from this.
I also want to add that work gives money and in this day and age, even for social work one might want to do, one needs funds. Money thus earned can be given for various charitable causes thus giving a tremendous sense of satisfaction and well being.
I therefore strongly believe that one of the important reasons that people work is for money for themselves and for their family, there are many, significantly more important reasons for working and these are the ones which actually keep life