If you have a website but it is not mobile responsive (meaning a mobile version of the website easily usable on a smartphone), then you should consider designing and coding a mobile version on your website.
Users are increasingly on mobile: Users on mobile has recently outnumbered users on PC.
Google’s new “mobile-first” policy: Google recently announced a “mobile-first” indexing policy, where Google has started to use the mobile version of a website by default for crawling, indexes and ranking.
In short, if your website does not have a mobile version, you should get one. Otherwise you are missing out.