I thought that was a classic red flag?
While I often just pack a carry-on bag for weekend trips, anything more than 2-3 days I'm checking a bag. I don't have to pay for it, my bags get priority-tagged so I don't have a long wait at the other end, and I've had to reroute due to weather at a connection twice in the past year, both of which I knew about before arriving at the airport.
So of the arguments raised against checking bags in the replies further down, none of them actually apply, and checking a bag means less stuff for me to lug around in the airports.
The choice of whether to check a bag or not is, thus, dependent on the specific passenger, the specifics of their trip, etc., and it is irresponsible and flat-out wrong to suggest otherwise, especially in such a "this is right and everything else is wrong" fashion.
I used to routinely fly with it on my person. I'd take it out of its sheath, put it in the basket for keys and change and such at the metal detector, and hand that to the uniformed agent standing there. I was never once challenged for this, or even looked askance at.
Your arguments are perfectly valid for some, but this is isn't a case of "this method is obviously right".
That's not so true in Europe, where many airlines have a quite strict size and weight limit (e.g. 8kg @ 55cm x 40cm x 20cm)
Sometimes you can pass people in the standby priority lines if they have bags.