Launching a website and not promoting it resembles owning a car and never drive it
It is necessary you ensure that search engines find your website. How? There's a lot of options. Each one of them makes for a higher exposure of your website, hence the number of potential customers increases.
First of all an optimisation is required so the website gets indexed properly in any of the internet search engines. Then you can choose between conventional methods such Google Adwords, external link,etc. or other more unconventional ones.