Answer:
1. Job shortage
Reason being there are few jobs in the market for teachers and thousands of graduates are entering into job market every year.
2. Career Expectations
The field he choose is based on his career expectations, as his thought process indicates that.
3. To engage in lifelong learning
Personal fulfillment is possible only when you feel you are learning new things and ways to do your work better. If you are getting new skills on job then you will feel fulfilled.