Was prescribed this for insomnia. 5mg no problem, which is why I...

I have been on Xanax for over 15 years, and at most take 1.5 mg when I am having a severe migraine which shoots my anxiety level off the charts. Otherwise, I take .25 or a full.50 tablet. I don't understand why doctors prescribe 5 and 10 milligrams to patients. This sounds so over and above what anyone could take and function! Xanax is not a sleeping pill, and to give a patient such a high amount put you at risk of severe side effects and dependence.