thats mainly because apple for the most part did not use hardware with temp sensors on them. now many cpu upgrades do have sensors in them, and they come with software to monitor them. also, some hard drives have sensors too. i was once lucky enough to have 3 that did. but one died, and i replaced the other two with one big one, which doesn't have a sensor, so i no longer can tell how warm it is in the case. you can always buy one of those room temp monitors that have the remote sensor, and stick the sensor in the case, and the display on the top.