How do you know that they don't?

Good question!

When I worked for the University of Texas, one of my students went to a local gourmet grocery store and got a $5 off coupon because she found fruitflies in her fresh fruit juice. It was printed in blue on a green background. Someone made a comment about how that would keep someone from duplicating it.

I said that it wouldn't be that hard to copy it. I was challenged, and spent the rest of the afternoon trying to exactly duplicate the storemade coupon. After a lot of trial and error, I was able to create over $100 worth of fake coupons. Just to see if I could do it, you know? No one could distinguish the copies from the original.

This other student, in an act of unbelievable stupidity, took them and tried to cash them in all in one shopping trip. The store probably handed out one or two of the coupons every week. This jackass brought in a handfull. They laughed at him (and complimented him on the forgeries.)

When you worked for the University of Texas, CC, you had way too much spare time... :)

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It's so much easier to work customer service or managers for the freebies.
i just got 15% off an order of flippy dresses as i typed this.
Yay, new clothes for once.
And should they not be sexy enough, be sure i shall be working that free return credit bonusing.

It's something to do with the ever decreasing amount of fossil fuel left on the planet, I believe.

When you worked for the University of Texas, CC, you had way too much spare time.

My MetaFilter history is a testament to this fact.

If you have a decent colour copier (and lots of workplaces have them these days), you can reporoduce most of this stuff without even the need for a computer.

Every time I go to an expensive fundraiser or concert or enter a raffle, I look down at the ticket in my hand and realize how easy it would've been to scan a legit one and make a fake.

Why don't I do it? Eh. Usually I believe there's a value to actually paying, and even when I don't, I have to live with myself, and I think my time is better spent on other things besides photoshopping my way out of a $25 or $30 charge for something I want to support anyway.

Yeah, I think that Steve Jobs said that when you pirate music you end up paying yourself about three bucks an hour by the time you've culled out the junk and taken into account searching time, etc. and I actually agree with him on this one point. Plus, I have a healthy sense of guilt over something like this, but less guilt over things that are probably worse, like getting my electricity from coal that was probably extracted from the mine that collapsed in Utah.

Forgery is a serious criminal offense. If you get caught by someone who wants to make an issue out of it, you're looking forward to a lot of trouble, probably more so than if you had been shoplifting. I imagine people usually forget this.