@Devoutspoken and @Beezknees, it's great that you've never had to deal with a serious medical emergency while drinking (or otherwise), and I hope it stays that way. But your method (? for want of a better word?) relies on you being lucky every single time. You only have to be unlucky once for the shit to hit the fan.
Also, it isn't just about being able to drive to the hospital. It's about being of sound mind to properly assess a situation, decide what actions to take, and then carry them out calmly and confidently.
For example, could you successfully take and read a temperature, give the correct medication dose, clean and dress a wound, clean up vomit and remake beds, remember to check on them regularly if taken ill, etc.
At the more dramatic end of the scale could you get your kids out of a burning house, see to a choking child, take a pulse, accurately explain their condition to 111, decide when it's time to throw in the towel and call an ambulance, arrange for someone to care for any other kids while you go to hospital, etc.
Obviously I know full well these scenarios are unlikely! It's up to each person to decide what their own limits are and assess the risk. But for me, I'd rather stop at say 2 glasses of wine and know I could do all of those things if I needed to.