I always thought that companies like using rebates because more people would buy the products. But in addition to that, I am sure that only about 50% of people actually fill out the rebate forms, so the company doesn't have to pay out a rebate for each person that buys the product.
DIRECTV had a rebate when I got the HD DIRECTV DVR. I haven't gotten around to filling it out. Most companies will just let the rebate expire. But DIRECTV has sent me two letters reminding me about the rebate, and actually included the rebate form again.
I wonder if DIRECTV got in trouble with not fulfilling rebates in the past.