Why surgery after DCIS diagnosis?

I had a mammogram about 5 weeks ago. Since that time, I've been back for more testing and physician evals maybe 5 times. "its probably nothing, but...." I keep hearing, then I'm back for another test or consultation. I had a second mammogram, then an ultrasound, then another mammogram, then a needle biopsy, which came back positive for DCIS (they accidently told me LCIS first). From everything I read, DCIS isn't serious. But they brought me back for another consultation, and now the surgeon wants to go in and take the whole area out. Then, depending on the results, bilateral mastectomy. I don't get this. I have no risk factors for breast cancer. None at all in my family. I'm so discouraged and depressed. The surgery isn't for weeks, Then wait for that pathology. Then what? Just one more test...?!