If you have web site, then in 99% of cases you need an extension. Why? There are 3 main reasons why you should have your own extension:
Extension will add a new way for a user to interact with your site.
Extension is an excellent bookmark. Once installed, it will always remind for a user that your site exists and that he can visit it. It is much more better because a user will always see your icon in his browser.
Millions of users every day searches for some extensions in Chrome Web Store. They can find your extension there and become your users too.
Please contact me for more details and project price before making the order. Thanks!