I liken "common sense" to "self preservation." So in the interest of self preservation, maybe one should not pet the big toothy animal. In the interest of self preservation, one should not consume poisonous laundry detergent. The two big hijacks to common sense/self preservation I see are 1. actual ignorance (like, the person is generally slow on the uptake in everything) and 2. willful ignorance. Like the person above motorbiking through the fire...they have the "common sense" (and likely the sad experience) to know it's dangerous, they're just choosing to ignore it and do it anyway.