Would highlight following reasons based on my experience:
- Wears multiple hats - marketer, designer, sales expert, business analyst, …
- must learn delegate and educate others to avoid becoming a bottleneck
- Must be domain expert so others and teams would trust in decisions
- Defines demand of investments into development
- Has to be perfect communicator as needs to clarify and negotiate important priorities and delivery dates
- Has to love his product and be passionate about it
What is your opinion?