Landing Page vs. Home Page!

Most experienced internet marketers say that if you advertise in pay per click search engines, you should have a landing page for driving the pay per click traffic to it. This landing page is different from home page and should be just focused on selling the product whereas the home page should be optimized for search engines and so is not good in generating sales.
They say home page is not a suitable page to drive the pay per click traffic to it and you waste money if you do that. It means a page that is optimized for search engines can not generate sales.
I don’t agree with this idea because if optimization disables the home page to sell the products to the visitors, so the traffic it receives from search engines, will be useless. So why should we optimize it?
What do you think?

Original post by Vahid