> let's get down to the facts. what is this tag practically needed for? it doesn't affect anything

It shows that there isn't anything missing from being mapped. If there's no toll tag, then it's unknown whether there is a toll or not (whether there's no toll or it's not been mapped yet). It's the same reason why StreetComplete creates so many =no tags.

I think it's a really good idea to show if there are tolls on every single motorway and expressway in Poland so that there's no confusion.