Then you take your cellphone out of your pocket. It's not that.
Then your keys.
Then your change.
Frustrated, embarassed, and completely bewildered at this time as to why you're still setting it off, you'll often still get through with just a hairy eyeball after they've seen enough of your stuff that they can tell you're probably not shoplifting, but it'll happen again, and again, until one day you accidentally stumble across the tag.
Trackerpants. They're out to get you.
(a common contributor to securapathy among shop staff)
"Oooh, look at that guy emptying all his pockets, what do you think he's got?"
"There's no security guard around, he's doing it all on his own. Looks like a classic case of trackerpants!"