From the article:

Another reason is that it’s much easier for the TSA to screen checked bags than carry-ons, and airlines keep discouraging people from checking bags.

Why is it easier to screen checked bags? 90% of the time I fly, no one opens my checked bag (at least, there's no TSA card inside, and the TSA indicator on my lock doesn't show it was opened), so if they check it at all, they must use some kind of scanner -- can't they use that same scanner for carry-on bags?

If screening for banned items makes it too hard to screen carry-on bags, then maybe they could trim down the list of banned items to a more manageable level.