Another issue here is that, in addition to taking a bunch of time to build these presentations, there are piles of other demands on a prof's time. If they're a

Another issue here is that, in addition to taking a bunch of time to build these presentations, there are piles of other demands on a prof's time. If they're a pure instructor, they have three or four other classes to teach, papers to grade, etc. If they're a researcher, they've got maybe another class or two and a strong obligation to produce world-class research, or else their teaching load will go up... The other issue is that presentations with shiny graphics probably aren't the best way to teach, either! I can give the best lecture or presentation in the world and still have a room full of students who couldn't reproduce even a tiny bit of it. The reason for the slow pace of lectures is to break up material into small, reproducible bits: we want students to understand the ins-and-outs of the cross-product, rather than just leave it as another wikipedia link to follow when there's time later (ie, never). That said, good course design will have some 'overarching themes' or big examples that are returned to time and time again, filling out more details as students have more depth of knowledge. This is often missing in, eg, intro calculus courses, though there are exceptions.