There are many reasons to be obsessive about always sharing credit with everyone who helped you.
1. You show you care. That’s the essence of leadership.
2. People appreciate it. So, they will want to work with you and care for you. It feels great and it shows up in performance reviews too.
3. You set guardrails against becoming a world class jerk. People aren’t born jerks, they become jerks. And it is hard to think too highly of yourself when you write that thank you email and realize the list of people to thank is longer than you imagine.