Here's a list of the reasons why :
1. They're funny
2. They help others
3. They understand difficult people
4. They move their asses
5. They're able to interest others
6. They trust people easily
7. They like people
8. They're more sociable
9. They're never tired
10. They aren't boring
11. They act like they were everyone's friends
12. They're playful
13. They're harmless
14. They're sweet
15. They're more able to appreciate the world
16. They aren't picky
17. They are aware of needs for efficiency
18. They aren't stingy
19. They're able to lead people without playing assholes
20. They're easier to please
21. They motivate others
22. They improve others' self-esteem
23. They don't educate children just by spanking
24. They're empathetic and sincere
25. They're able to sacrifice themselves for others
26. They have a larger range of emotional states
27. They're modest
28. They're aware of others' needs and desires
29. They're good sellers
30. They're able to behave themselves
31. They aren't conservative
32. They are the fucking S-H-I-T !!!
33. They are the fucking S-H-I-T !!! a second time, because redundancy is cool ; everything that comes from extraverts is cool
You may continue this list as you like. This list is open-ended.