ATC wants you on their frequency for a reason. You may be too far away for tower or the airspace is busy and approach needs to keep everyone.
The point of the original post is that the purple box is your responsibility to make that turn. The controller will get you within 30 degrees of the final runway heading. Its up to you to line up. ATC will never line you up perfectly with the runway. This diagram shows a pattern where approach gives various turns, Then for final you get two 30 degree turns. The turn to final and lining up with the runway is all on the pilot.
Once approach sees you making the final turn, they will instruct you to contact the tower. If you forgot to turn and there’s a line of planes behind you, the controller may give you a missed approach (cough to the back of the line)
This is one reason we emphasize looking at the messages at the top instead of waiting for the audio. Sometimes the audio can be seconds later and will put you out of position.
PS… Also a good reason to be < 200 kts for that final turn. Going to be hard making that turn going 249kts.