A "Landing Page" site is the modern-day version of the sales brochure.
You give the customer a glimpse of what you have to offer and explain why they should choose your business as their provider.
Unlike a sales brochure, the information on your site can be updated and changed for considerably less than a new print run. In addition, the updated information is availble to your customers as soon as your site is updated.
Keeping your customers informed of upcoming events and sales or changes in pricing is good business practice.