Why did job make me full time?

For the first half year, I've proved helpful at a shop part-time, but many weeks I've proved helpful 40 hours. The administrator just provided me to become fulltime. Most of the workers are part-time, and have not been requested to become fulltime. I never pleaded to be fulltime. He just requested me instantly. In the last he has said I'm doing excellent work at the shop. Is that why he requested me? Because he believes I'm a good employee? Full time job is helpful for a college student, when he graduated, his advantage is work experience. I favour a student can take part in social practice to steel himself.