Most exit doors are designed so that the cabin pressure forces them to stay closed, so they cannot possibly "blow out." The plugs were designed with cost savings in mind, which is why they did not bother engineering such a safety feature into them. No way I'm passing up on extra leg room for the infinitesimal chance of an incident. While it seems like this fact gets beaten to death, it is worth repeating: you are exponentially more likely to be involved in an accident on the way to/from the airport than on an actual plane.