Your best candidate might be interested in your job, but how easy it is actually to apply? In the modern market if it takes more than five minutes and you ask for attachments like CV, you will lose a lot of potential candidates because of an old fashioned process. Especially when internet usage is moving more and more towards mobile phones instead of computers. Your best candidate might also not yet make a decision that they would want to apply to your company. They would like to talk to you first. Lead generation 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 want to apply or not.