why are people bipolar

Why people are afraid of bipolar people and label them as "insane"?
Although not diagnosed, I realize that extreme mood swings and that is affecting others, so I'm starting to receive treatment. I lost a dear friend of nearly 10 years because of my emotions. I wish people might be more understanding about mental health.
I have this same problem. They have not been diagnosed, but I'm almost 100% positive I have depression bipolar. I will not be diagnosed for fear of being labeled. I do not want others to think or believe I have to "take my medicine" to be normal or happy. That's a problem.
Two Bi-Polar people