Most lenders, bank or credit union managers still have to go by their "gut feeling" about a person when it comes to lending money. A credit score can only say so much, and many people have blemished credit from something that was beyond their control. Does this make them an automatic credit risk? Probably not, but if you are a complete stranger to these people all they have to judge you buy is the numbers. If you have bad credit, that dosn't necessiarly mean you have no money either. Something that happened 4 years ago when you were between jobs effects you now. Again, if all they have is the numbers then you are a high risk and you will get an intrest rate accordingy or no loan at all.
Sure there's more to it than being friendly, but it has to help. IF they know you as a person and how you are then the numbers won't matter as much. It also helps to have good upstanding accounts at where you are getting a loan. If you maintain a good balance in your account that's another plus.