Athough the main purpose of the parade is to educate people about the negative effect of slot games or gambling in general but on the other side, such a parade can be seen as a free advertisement for the slot game.
Simply because it is in public places, not all people who watch the parade are gamblers and I'm sure there are so many underage people who watched it and might be curious to know about what is being presented by parade because they never seen it before.
My opinion, it is something with a good main purpose but with a bad way, because there are many other better ways to educate people about gambling.
Slot/gambling education should not be done in public places like this IMO.
I agree that the other thing you mentioned is true, like that not all people who are in the parade are aware of the gambling they are showing, and it is also true that it is also a kind of advertisement method done by those coordinators.
It looks like I also think that the people there know different sugars compared to the gambling they advertise, like slot games. It looks like the internet is also weak in that place, or possibly there is no internet in that place, if I'm not mistaken.