Your doctor is probably only suggesting what seems appropriate for your particular case. As you probably know, the exact reasons for low back pain are often mysterious. It's possible your friend had at least somewhat different circumstances. Your friend's doctor may have been concerned about more serious problems, like a spinal infection.
You may be interested to learn, however, that X-rays often don't help doctors determine the cause of low back pain, even when the X-rays are medically appropriate. Talk with your doctor about your concerns. You can never have too much information.