Swp memory no longer being used Macbook Pro Mid 2015
The default macOS setup has a dynamic swap size. This means that even though htop displays "0K/0K" it doesn't mean that the total swap capacity is 0, or that swap is disabled. It just means that right now, there's no need for swapping (and that is a good thing).

If later memory usage means that swapping is necessary, the operating system automatically increases swap capacity. This is ofcourse limited by the amount of free disk space on your computer.