Some teachers seem to feel that students who don’t pay attention in class, or that don’t show up, are wasting our time.
But it’s we who are spending their time. And if they don’t show up, or do something else, they apparently feel they can get more value out of that time than they see us to be offering.
Now, they might be wrong about this, but odds are that at least they’re acting rationally in according with their current judgement. If they don’t see that they’re wrong, you can’t blame them for acting against their own interests.