Thermocouples have been known to go bad. Depends on what you expect out of your knives I guess. Can't believe anyone wouldn't test the edge.
As I said, small flukes do exist, and that includes cases that thermocouples fail. I didn't mean to say that one should go about it blindly, which is why I recommend getting at least a hardness file set. I use a set on every blade to ensure I'm within a given range and every couple months I send a coupon with my buddy who works at detroit deisel, and their metal lab tests the hardness for me. So far the deviation has been more than acceptable.
A bad edge will be discovered at some point before it leaves my hands regardless. I personally don't like to take the risk and would rather peel a pair of scales off in the case of it not performing as intended. Doing due diligence and spot checks periodically leaves me with the utmost confidence in my blades. Many makers do it this way, so it seems odd to me that this surprises anyone.
A cut on the hand can me more than superficial. Tendons and nerves are extremely exposed in the hands and damage in some cases means permanent disability. This could not only effect your hobby but your career, your livelihood, you marital situation, or all of the above. I'm a bit of a safety nazi, but I have seen first hand what complacency can do and have personally witnessed how bad the damage can be because of it. It only takes one slip up in the wrong way and you've lost the use of most of your hand, or worse.
I was working with my brother on a concrete crusher and he operated the plant. It was a long day and we worked into the dark. During the end of day inspections my brother made a mistake and slipped doing something he did every day for almost a year. The massive rotor sliced his hand severely and crushed/broke 3 metatarsals along with severe tendon, muscle and nerve damage. The only thing that saved him from losing his hand was his index metatarsal, the only bone that did not break. Obviously this is a worst case scenario in a very different circumstance, but my point is it only takes one instance of complacency to make a mistake that will influence the rest of your life decisions.
Sorry to be so long winded, but I hate having to explain why I do things in the safest possible fashion. Accidents don't "just happen" and most are avoidable. I try to do my best to avoid them.
Justin