Your best candidate might be interested of your job, but how easy it is for him to apply to you? In modern market if it takes more than 5 minutes and you ask for attachments like CV, you will lose a lot of potential people becouse of an oldfashioned process. Especilly when internet is usage is moving more and more to mobile phones instead of computers, you cannot ignore this fact.Your best candidate might also not yet make a decision that he/she would wan't to apply to your company. They would like to talk to you first. Leadgeneration is simply that you offer them some alternative solution like filling a test or talking to a bot for getting to talk to you before making the decision if they wan't to apply or not.