Why won't anyone hire me while I'm attending college?

I'm entering my 3rd year at my University. Within the year of me being unemployed, I've been on 16 interviews. Over 1/2 of those interviews I've had 2nd interviews, but the question of me staying at the job after I complete my degree always comes up. I ure all employers that I'm looking to be with the company long term, but I never get the job. Add insult to injury, the ad for the same job usually reappears after the employer doesn't keep the person they initially hired. What am I doing wrong? Should I omit that I'm in school on future applications?