[Serious]What's the logic behind a holster with an extra magazine slot?

I see holsters that feature an extra slot for a magazine, like these:http://ift.tt/2b5sQdi If you need to draw, why would you want your reload to be on your strong side? What do you do if you have to reload - change your firearm to your other hand? Reach across your body with your support hand? via /r/CCW http://ift.tt/2akPvoR