Usually companies that launch some kind of product would love to brag that they say sold one million units in a day. Essentially, for people on the outside you get the impression that it must be good to sell that many units so fast. Hence, it just builds up the hype to potentially sell even more.
There was a recent launch for a product and I was thinking of buying it it in the near future. Funny enough, it did also use this strategy though where if you bought the item right on the launch day and then registered it with the company that you would receive some kind of reward. You literally had like one day to do it.
Even I admit that kind of swayed me a little to want to buy it right on the launch day. However, I ended up not as I figured I would probably save more when there is a sale and with the money I save that free item is obtainable for less.