So, SMB owners then try to find some other way to get a presence, many of which make it difficult to use your own website. Facebook, for example, is setup in a way where your FB biz page is highlighted, but the url to your actual site is obscured and buried.
Aside from your examples of Facebook, Instagram, and Twitter...I've also seen SMB's move their ecommerce sales to Etsy, eBay, Amazon, and the like.