It also allows you to have "1 hour" classes that are at 10am and 11am, and you aren't forced to leave early or arrive late. A 5m gap isn't enough for huge numbers of classes in many campuses.
All my classes were 1.5 hours long. Yet professors still regularly chose to introduce new material on days with back-to-back classes, leaving standalone classes for practice or “less important” topics.
Almost exactly as much as one that's 55 (or 60) minutes long but many people are late to.
But yes, "1 hour" is fairly short for any deep topic progress. I vastly prefer classes that are 2 or 3, it gives time to have questions and not be in a blind rush.