Need help with this, still bipolar?

i'm really new to this whole thing, so i'm not even close to qualified to offer my opinion... but no one else is stepping up, so here goes!

it seems like a majority of people whose Dx changes are being told they're bipolar after years of believing they were unipolar. it also seems like this happens when someone finally notices that the depression is cyclical. if you're cycling (even if you never reach a state you would call manic), i don't see why anyone would want to tell you you're unipolar. are your treatments not working or something? has it been a long time since you cycled upward? is there more to this story?