Because they work through an entirely different mechanism, basically. Ethanol (and other similar ones like chlorine) works by disrupting cellular life at a pretty basic level, destroying protein and membrane structures which means that you can’t really develop a resistance to it. It affects us, too, though the relative amount of alcohol we’re ever exposed to is far lower then the relative amount that a bacteria is exposed to (getting thrown in a pool full of alcohol would kill us, as well, though our skin provides protection), though it can and does kill a number of our cells even under normal situations.
The ones under investigation, triclosan and triclocarban, work very differently. Specifically, they target several widely occurring pathways in bacteria, fatty acid synthesis and membrane construction. While they have a real mechanism of action that can and has been tested, the amount used is the important part (“the dose makes the poison”), and it seems that the amount most manufacturers put it may not be enough to actually kill bacteria. Also, since they target specific cellular pathways (unlike ethanol, which mostly just causes wholesale destruction), cells can develop resistances by simply rerouting those pathways, which is another real danger, especially when antiobiotics appear at a level low enough to kill everything.