That's not true in all cases, Ibby. For a long time, Siamese cats have been selectively bred as human companions. They are very dependent on human company and pine and become depressed if separated from their owners/companions. They come when called, know their names, play fetch, etc. They're smart, but the reason they do all the aforementioned things is that they are VERY attached to people. They will jump into the bath or shower with you if they feel neglected (i.e. if they didn't get to sleep with you and keep you up all night kissing your face)!
Some cats don't give a fuck - but not Siamese. They rock.