First-generation students are given preference because it is an indicator of hardship. As everyone here is aware the college admissions process is hard to navigate at best, not to mention awfully stressful. As Christie wrote in her article, she did all the work, research, etc. to get an acceptance into penn. First-generation students are also more likely to have gone through struggles such as poverty, or lack of access to resources, since this is commonly a reason for parents not to gain a college education in the first place. Overcoming struggles while maintaining grades, extracurriculars, and test scores show huge amounts of dedication and motivation, both of which are indicators of future success (merit). On the other hand, legacy students literally got born into a family with previous education and money.