TV ads usually don't mention pricing for national brands. Local ads like circulars are generally for just one store anyway. All of this would be low effort to do. The only reason they don't is it tricks people into spending more than they want.

Prices are printed on packaging for many things too, books, magazines, bags of potatoe chips.

So then stores would have to cover the manufacturer price with a higher one just in their store. Which is a waste of time and material if you can just condition a population to ignore the price jump at the register.