Employers never need to answer why they hire or don't hire someone.  Many times they don't even know why they "pulled the trigger."  They don't owe you a reason for hiring you or saying "no." Your job as an applicant is to make sure they know who they are interviewing and that you actually care about the person(s) you will be working for... that you seek collaboration and synergy in your work day and all the team members will benefit from your being hired.

Every applicant knows that by hiring you, the company will experience benefits (financially, systemically and the company's enhanced reputation) but even more important, is that the hiring manager(s) will benefit personally (less stress on the job, more time for him/her to spend with their family and a more attractive career path for them should you be given the opportunity to work for them.