Update on December 29, 2020
Currently we access the internet from almost any location thanks to our mobile phone, and this is due to the adaptive design of websites or as it is also known as responsive, this type of design allows the creation of web pages that adapt to the screen sizes of the devices in order for users to view the content from their computer, tablet or mobile phone.
A responsive web design aims to improve visualization regardless of the screen size, responsive is important and should not be missed because if the content of your site is convincing for users (it can be a blog, a sales site , a news page, even a cookbook), they themselves will share them on social networks generating traffic on your website, but if your site is not responsive, users will have to expand and decrease the content to see it well; that is something that will make them leave the site without thinking twice and will hardly return and when I say they will hardly do it, they may come from your laptop, but let's face it, not all of us carry our laptop everywhere, what we do carry is our mobile or tablet since they are small, practical and more portable; Tell me where are you going that you don't take your mobile?
That your site is adaptive helps and even improves SEO, increases your presence in social networks, is a ranking factor in search results (it has to do with SEO) and above all users enjoy an optimized website
Currently there are tools to create websites such as WordPress, PrestaShop and Opencart in which you can buy plugins to make your site responsive, if you are a developer you can find already predefined libraries that you can modify, and you can even develop responsive through CSS.
Now you know that yes or yes, your site has to be responsive!