Well, the title is almost self explanatory. I am in a graduate school and have two professors this semester both of who are telling me that they are not following any particular book, and yet when I pressed for some recommendations, they came up with some books. I got them from the library and started reading them, only to discover that they are not really using those books. Somehow, I found out the books which they are actually using and it turns out they are copying each and every example from that other "a little less known book" in the class. The assignments are also exercises from that book.
Now, my point is why do professors feel the need to lie about such stuff? I am not someone who can take good notes, so all I try to do in the class is understand what is being taught, and then go home, read the relevant section from the book and then make notes later, at peace. I am kind of pissed off at my profs, and yet I think getting some different perspective might help, and so, I'm asking here. Do a lot of professors do that? And why? If it makes any difference, I am at one of the best institutes in my country, and the professors are pretty distinguished researchers world wide.