But I don’t think the advertising is that big of a reason. Most of the ads I see the print saying “after rebate” is not that small, perhaps California law requires it?

They do want you to think you will get the product for the low price, and of course, much of the time you can, though they know that a large chunk of people will not.

But in fact, rebates would still be used even if everybody who cared got the rebate, and those who did not care did not. That is their actual goal, to offer a lower price to heavily price sensative users and a higher price to those who are not. I think tricking people into believing they will get a rebate when they actually won’t follow through perfectly also plays an important role, but it’s not essential.