For a lot of businesses, a website receives way fewer views than any one of their top-3 social media sites.

I’ve seen a lot who are still paying for a site but rarely bother to update it. All the traffic’s on Facebook.

It is not just 15$ a month. You need to pay someone to develop the website in the first place and then deal with all kinds of issues that eventually arise (updating the underlying framework and/or getting hacked and dealing with the consequences, solving random stuff like expired SSL certificate, etc.).