Shyness has become social phobia in large part from the advertisements from pharmaceutical companies and the doctors who promote their products. Pharmaceutical companies have a vested interest in expanding the definition of who has an anxiety disorder, such as social phobia. Their prescription medications for social phobia are what they are trying to sell, so if more people are diagnosed with social phobia, then the pharmaceutical companies get more sales of their products.
So what we once saw as shyness, is now social phobia, all due to greed on the part of pharmaceutical companies and the doctors who are paid well to promote their products. But the fact remains that shyness is much more common than social phobia, and most people with social anxiety do not need to take prescription medications for it.
Social phobia is rare, and shyness is common. So let's use our common sense, and quit medicalizing and pathologizing normal human traits such as shyness.