HR professionals usually have to search through hundreds of resumes to find the best candidates. Our minds have limited capacity to handle big information, so our brains create shortcuts to make decisions quickly.
It makes HR managers go with their gut feelings, which leads to unconscious bias during the hiring process.
Every single detail on the resume can be a deciding factor whether you get selected or not. A mailing address can indicate an undesired location. An email address containing unusual names can turn off the recruiter, or even the college name can be perceived as a non-pedigree school.