In my childhood, being invited to a party meant that you get to eat snacks, sweets, candy and cake placed on the table. And that you get to annoy the hell out of adults by being loud and jumping around, while everybody else is doing the same.
This was considered good enough, without the need to also get your personal bag of candy.
@Stephie I meant about geographically localized, is it common throughout Germany?
Not only haven't I been at a party which included it, it is also the first time I have heard somebody referencing the tradition.