Sorry I'm not implying I have any practical reason why this is the case. Its just how it was when I was in school. But I'll say where I went to school, and I h

Sorry I'm not implying I have any practical reason why this is the case. Its just how it was when I was in school. But I'll say where I went to school, and I hear its even worse now since enrollment in STEM is way up, there were often multiple thousands of students every quarter wanting to take just one class, so they split it up because we simply didn't have lecture halls with enough seats. There would often be 3-4 classes each of 500+ students all full, and still students struggling to get in due to the maximum amount per course. Usually there was around two teachers splitting the sessions, and they also have their other more advanced courses and/or research. So its probably just practicality in terms of their time and resources. This wasn't an issue with more advanced courses where there was usually only one teacher per semester offering the class.