That can make sense when you're coming from a tiny side road onto a major busy highway.

It doesn't make sense to delay thousands of cars on the highway by 30 seconds so that one car can cross it a few minutes faster. Better to make that one car wait 10 mins (and perhaps by now it is a queue of 3 cars), and save 30 seconds * thousands on the main road.

Other countries normally build bridges or highway merges to avoid this problem.