Clever tricks lecturers use

Our lecturer played a clever trick on us on Monday. I'll set the scene for you.

So our lecturer has been talking for about an hour about Team Goals and Communication. There is a quiet rumble at the back of the lecture theatre as people talk. You can sense a feeling of restlessness from the back half of the class and a feeling of restlessness from the front as we try nad concentrate over all the whispering and muttering going on!
It's two o clock (this is a two hour lecture by the way, 1 to 3pm) and our lecturer looks at his watch and says.
"Okay I'll give you a break now. We'll carry on with this in 5 minutes." The guy behind me says to his mate:
"He does drag on, hurry up!" Well with respect this is a 2 hour lecture so he's not going to talk for just an hour and give up is he?!
The majority of the back half of the class geta up and leaves. they think the lecturer thinks they're just going to the loo or to get a coffee, but they're taking their bags and coats with them. They're leaving, for good.
Once everyone is out the door (two minutes later) our lecturer says,
"Right now they've gone we can get on with this. What we had in the first hour was an overview. Now this is the stuff really related to your assignment and exam." Brilliant! He's saved all the important stuff for after the whsiperers have left! Now they are severely disadvantaged for the exam and our essay and it's all their own fault. No one came back into the room after 5 minutes, seriously no one! Just us front half who actually want to learn here now!

This has been botherig me for a while now. Lectures are compulsory at uni and if you miss the odd one through illness or family or traffic problems so be it. But to not want to listen in a lecture, isn't the idea of uni that you are supposed to come to lectures to learn? Why are you at uni if you don't want to come to lectures? It's a waste of time AND money. It seems sad to me that some people are happy to waste their parents money like that. Or worse if you're paying to be at uni, your money!
This excellent article shows me I am not alone in pondering this mystery.

http://www.independent.co.uk/voices/comment/in-holland-university-is-a-reward-for-hard-work--why-do-british-students-think-so-differently-8510200.html?fb_action_ids=4601237030534%2C10200801185854700%2C10152582213910597%2C10152582211765597%2C10152582200990597&fb_action_types=news.reads&fb_source=other_multiline&action_object_map=%7B%224601237030534%22%3A132185716957105%2C%2210200801185854700%22%3A132185716957105%2C%2210152582213910597%22%3A10151660949548484%2C%2210152582211765597%22%3A593759220651742%2C%2210152582200990597%22%3A434264533310859%2C%2210151536413314948%22%3A434344563306541%7D

The comments at the bottom are anoying. They're basically saying that anyone at a 'former polytechnic' or former 'teaching training college' doesn't want to work. Not true. the majority of us do.
I know this isn't my problem and I shouldn't be worrying about it. I'm not worried just curious as to why some poeple think this is the right way to behave at university.