Trading

I applied through my school's career search service and was given a first round on-campus interview. The first round interview lasted 30 minutes with questions on mostly conditional probability. Then an on-site consisted of 4 back to back 30 min interviews involving more brainteasers that is heavily probability and algorithms focused. Each interviewer also asked in various ways the 'why I want to become a trader?' question. In the end they told me my problem solving abilities were adequate but was unsure of my interest in trading. I guess I should have prepared the 'why trading?' question a little better.