It's been years since I've had a discount I could offer over PPC. I remember when I was a young search monkey, that companies would offer the coupon code directly in the ad copy. However, an inspection of ads on various queries, I don't see anyone doing this. I want to, because of course a concrete offer should certainly help CTR right?  But, not finding any referent examples of other companies using the coupon code freaks me out. Is there a drawback to posting the code directly?

Haven't worked with discount codes in years. Researching the ad copy I found very few sites putting the promo code directly in the ad copy. I thought this was a standard practice for increasing response. Do you know why companies with active promo codes don't use them in Adwords copy?