The reason for this is simple: the surgeon knows that your body is already fighting an infection, meaning your immune system is already somewhat compromised, and surgery always poses a further risk of infection and always makes a greater demand on your immune system. The doctor simply wants you to be as healthy as possible and reduce the risk of complications.
This is just one more example of the connection between your overall health and your dental health. It's unfortunate that health care creates a disconnect between your mouth and your body, and doesn't cover your teeth, but that's the reality.
Too many people discover too late that the source of many of their health problems is what's going on with their teeth--they have gum disease, or an abscess, and this is affecting their health in ways they don't recognize. What more proof would you need than a surgeon unwilling to operate on you?
Don't let it get this far, or anywhere near this. Find a dentist you love, see him or her regularly, and stay truly healthy.