Having worked with a significant number of undergrad and grad students on their job and internship search, and having many conversations with friends and former students, I have compiled a list of the most common reasons why people did not get the job or opportunity (internship or first full-time position after graduation):
1. Your resume was not written well.
2. You started your job search too late (most companies now start in the fall, and are all set by the end of fall). See The Best Thing To Do In Early Summer for Undergraduates: Prepare For Opportunities Next Summer.
3. You blindly applied to everything instead of making an effort to go out and network with a company that is one you know you would legitimately enjoy working with, and demonstrate to them that you're worth hiring.
4. You looked at the wrong places. The "usual suspects" in your field are never your only options.
5. If you just applied online, your resume and application was probably not read (related to #3 above).
6. Your skills did not match the needs of the employer; you have knowledge gaps.
7. You have little to no real working experience to show for.
8. You have little to no real tangible projects to show for. See Understanding Why Side Projects Are Looked At So Highly in Tech.
9. Something came across poorly in your interview including personality, body language, didn't answer the questions, dress attire, gave canned answers, didn't ask good questions, seemed dishonest, showed up too early or too late. More:
- You came across as privileged or arrogant or overconfident; on the other side of that coin too timid or unconfident.
- You were unable to articulate what you want to do (sounding like you would take anything, anywhere is a bad strategy).
- You didn’t do a good job of researching the organization and/or could not articulate why you wanted to work at that particular company.
- You couldn’t demonstrate what you would bring to the party that would be relevant to the position.
- You plan to only stay at an organization for less than a few years and you told them that.
10. You need more experience working on teams, learning how you can thrive in that environment.
11. You didn't fit the culture, didn't click.
12. You didn't follow up (within a week). This includes not sending a thank you note after your interview.
13. You couldn't tell your weaknesses or failures.
14. You didn't sign the offer in a reasonable amount of time. An offer is not forever.
15. You asked for too much or seemed too needy.
Last but not least, the worst thing you did: you gave up.
Special acknowledgements to Mark Bouchard, Robin Kahan, and Winnona DeSombre as some of the items were taken from them, word-for-word.