I’d post that straight lecture is a crap way to teach/learn. And the large auditorium classes that are common at most state Us are fundamentally broken. Interactive discussion is probably much better for most students.
At the same time, the time is given because not everyone will have time to read ahead of time. That 15 minutes at the start is their calendar block; think of managers who have back to back meetings all day.
It's not some referendum on people being careless.
The courses I never attended a single class for were reading screenshots of a textbook.