you are supposed to receive a stack of fapiao of equivalent face value. In the past 9 months I've never received more than one of these fapiao , if they even gave it to me at all. Also, the prizes are pretty small, enough that there isn't that much of an incentive to ask for these "lottery tickets". The largest "prize" i heard about (because i've never seen anyone win) was about the equivalent of $6 USD.
It used to be more common in the past: you buy something, and the fapiao (certified tax receipt) would include some sort of scratch off thing that was like a lottery; so you had some incentive to collect your fapiao and preventing the department store from low balling their taxes. Store owners are not supposed to recycle unclaimed fapiaos, that is definitely illegal, and many companies who follow the law to the lette…
To the gp, I usually don't get fapiao if I don't ask for it, but it sometimes comes. I always get it if I ask for it, or they offer me a Pepsi on the house or something to avoid giving me fapiao. So it's always in play, as far as I can see.