@RRoseshavethorns With steak, the bacteria lives on the surface of the meat, so that's why you can just sear the outside surface of the meat to destroy the bacteria and still have it raw inside. Mince, on the other hand, obviously can't be eaten raw because as it's minced, the bacteria from the surface is all mixed in.
With bacteria, it's not so much that it's there per se, and we consume it all the time. Even cooking to 75% doesn't always destroy it completely it just reduces it to a safe level, and that's the key point, a safe level. You might have cooked something, and any surviving bacteria are eaten, but the number (and its toxins) aren't high enough to cause illness. Where as if you give the surviving bacteria the correct conditions, i.e., ambient temperatures and enough time, it will multiply to unsafe levels.
When children touch things and put them in their mouth, they might be consuming bacteria but again not to an unsafe level. Bacteria on a toy, for example, most likely won't contain the right conditions for it to multiply to unsafe levels. They are more likely to pick up viruses though, which don't need specific conditions as they don't multiply.
The misconception is all bacteria need to be eliminated everywhere or you will get sick. That's not the case. Bacteria just need to be controlled in food handling to avoid its multiplication or cross contamination from raw to ready to eat foods.