They roll over things. Neat sounds happen while graphics pop-up like magic. Along the way, they figure out how to make the interface work. If only the audience really cared. If you are out to make money, the Web is a nightmare.
Users have thousands of opportunities to go somewhere else.
You have seconds to convince people to venture in and see what you have to say. With hidden buttons, you have just locked the door. You have just told your visitor that your site is a secret club and they had better waste their time figuring out how to get in. I am not saying that hiding things in your interface is always a bad idea. Sites that entertain users with games involving a mystery or puzzle are fun.