A large proportion of people who visit your website are going to arrive after undertaking a search with Google, Bing or the like. When they do, it's usually because they are looking for a specific product or service, the answer to a question they have asked, or to alleviate a worry or solve a problem.
If this visitor then simply arrives at a generic homepage, without specific references to their search criteria, you're likely to lose them very quickly! This is where it pays to have landing pages for key products or services, or perhaps a geographical location where appropriate.
Providing these pages let's the visitor know instantly that you are talking to them - about what's on their mind - and you are then much more likely to find them staying on, and engaging with, your website.
REMINDER: Addressing those key searcher concerns or needs means you can keep them with you!