Not only this, but the black/yellow kerbs actually work in keeping guests away from certain areas. I mean, in the end it's not the biggest deal at this very moment, as I'm sure it'll all be fixed at some point in the future, but it's one of my pet peeves having guests walking through scenery and other objects.
For this there are still barriers you can place underground. So the black/yellow kerbs are missing, but i feel they were really weird since they had this overflow mechanic: you can not walk here unless it is crowded, barrier fences just simply stop guests.