In the two decades since Amazon streamlined the e-commerce process, most retailers have followed suit with an online point of sale option, seeing no other way to compete.
As a result, about 70% of Americans (230 million) will make an online purchase in 2018, contributing $474 billion to total retail sales, according to Statista's Digital Market Outlook. As this chart from Statista shows, even as e-commerce sales gradually account for more of the dollars spent in retail, that continues to be a relatively insignificant chunk of an industry that made upwards of $5 trillion in 2017.
In fact, the first and only time e-commerce accounted for more than 10% of total retail sales was at the very end of 2017 — if it follows its historical pattern, it should be back at those levels some time this year.
It's important to note that "total retail sales" also includes the dollars made from motor vehicle sales, gas stations, groceries, and other categories that aren't as affected by e-commerce as clothing or office supplies. Without them, the share of e-commerce spending would be more like 20%, according to market research firm comScore, which is still considerably low.