LeadPages is *not* the same thing as your email marketing software, such as Mailchimp, ConvertKit, or Infusionsoft. LeadPages helps you get more subscribers, but does not allow you to send regular emails to your list. So, LeadPages can be used to grow your email list and then you can use another service to communicate with that list. Make sense? In that case, why would someone want to use LeadPages? Because they offer tons of templates to help you make high-converting landing pages and allow you to easily send content upgrades.
Of course, regardless of how they enter into your funnel, your goal as a marketer is to move them through the multiple stages that will take them from prospect to buyer. And once they're aware of you, you need to build their interest. To do this, you need to establish a relationship with the customer. You might have enticed them with a great offer (lead magnet) to grab their email address, but actually moving them through the funnel is a far greater challenge.
For example, when a customer finds you organically through a Google search for example, that means you have some element of authority. When you have authority, prospects are more likely to enter into your funnel because they know that if they found you relevantly, that whatever it is that you're providing must be of a great value. That's just the nature of SEO and organic search.
The first helps direct attention to the goal of the page -- for you to fill out the form -- in a way that's unobtrusive and feels less like a chore. The second gives this page an SEO boost (search engines will have more content to crawl) and assuages any worry from folks who need to know more about a piece of content before handing over their information, all while not distracting people from the chat window.