That's a great question, and one I get asked a lot! In my experience, the vast majority of outdoor trash cans, like the standard wheeled carts provided by many waste collection services, do not come with liners. You typically have to purchase bags or liners separately. These large, durable containers are designed to handle bagged waste directly, so you'd place your tied kitchen or yard waste bags inside the can. This helps keep the bin itself much cleaner.
However, there are some exceptions. Certain smaller, decorative outdoor bins or specific models from home goods stores might include a liner or a set of bags as part of a starter kit. It's always best to check the product description or packaging details when you're making a purchase. The listing will usually state if liners are included.
My advice? Assume you'll need your own bags unless it's explicitly stated otherwise. For those large wheeled carts, I recommend buying heavy-duty, large-size trash bags designed for outdoor use. They're more tear-resistant and can handle the weight and weather. For smaller patio or deck bins, standard large kitchen bags often work perfectly. It really comes down to the specific size and style of your outdoor trash can.