That's a great question, and one I wondered about myself when I first bought an outdoor bin. Generally, most standard outdoor trash cans do not come with liners or bags included. They are typically sold as a standalone unit. The expectation is that you'll purchase trash bags separately to fit the specific size and shape of your can.
This actually works out better in the long run. It allows you to choose liners that suit your needs—whether you want heavy-duty bags for yard waste, scented ones for kitchen scraps, or biodegradable options. A good-fitting bag helps keep the container itself much cleaner, prevents leaks, and makes hauling the trash to the curb a simpler, less messy task.
My advice? When you get a new can, check its gallon capacity (like 32-gallon, 64-gallon, etc.) and then buy a box of bags designed for that size. Drawstring bags are fantastic for outdoor use as they close up securely. Remember, using a liner isn't always mandatory, but it's a small investment that makes maintenance a whole lot easier.