Same reason nobody has to compel one to live their life’s purpose. If in your soul you’re a musician then nobody has to twist your arm to sign a record deal if the opportunity comes along
It would be downright hilarious to think Jimi Hendrix would need to be negotiated into talking about the guitar. Dude would probably talk music with you for hours and be stoked to recommend a book to his new roommate that respected him and tried to get along without kissing ass.
Demons are closer to people. If you understand human nature you’ll understand how to work with demons. That said, anything involving a sense of gratitude, duty, or anything you’d call the higher self is the realm of angels. They’re the altruists. Demons might help simply because they like you.
The one common ground they all absolutely share is they respond to self respect and sincerity. Angels even more so on that last one