So you want to add a shopping cart to your site. Do you really think this is a good idea? How about a "buy now" button instead of an "add to cart" button, so the customer can check out directly from the product page? What if that "buy now" button was powered by Apple Pay or Google Pay?
A shopping cart separates the PDP from the checkout by one additional click. Skip that click, and the whole purchase funnel will be shorter and faster. The buying experience will be much easier and your conversion rate will go up.
"That sounds great"—you might think—"but what if my customer wants to buy two or three products? They'll have to pay three times instead of one and they'll have a less pleasant experience".
I hear you, and you might be right. The good news is: you already know the answer. That's right there in your data. Check your order history for the average number of line items per order. The more it's greater than two, the more likely your customers are to buy more items within the same shopping session, so removing a shopping cart is probably bad. Instead, if the average number is closer to one, then you'll really accelerate the shopping experience for most of your customers, and the impact on those who buy more stuff will be limited.
If you're still not convinced, let's use your data again. Run an A/B test swapping the "add to cart" button for a "buy now" button on a subset of your site PDPs and measure what happens. It's easy and definitely worth it. Then you can make a more informed decision.
Or just keep them both. Let customers choose from two options: add to cart or buy now. With some personalization intelligence, you can even change the order of the two buttons depending on a customer's behavior or purchase history, getting the best of both worlds.