People who really have nothing better to do than make up silly rules.
At one time, you could NOT bring a lighter onboard, BUT, you could carry matches! Make sense?
You can carry knitting needles, but NOT scissors.
And with scissors, it all depends on where you are. I have had folding scissors taken away, kids scissors (blunt point) taken away, but a pair of full size (cheap Walmart) scissors go thru. Doesn't make any sense!