They just get paid less. Getting tenure is a gruelinbg process and even after getting tenure the amount of work can be overwhelming. Research, writing, publication, administration and committee work form the remainder of the work. Lastly, don't assume that the ability to teach college level students just comes automatically or that any one can do it. Students and colleagues today are much more demanding that that.
Professors do it for the freedom of deciding what to work on.
They do it for the psychic rewards of teaching. They do it for the love of creating knowledge and always working on something different. But, do not think that they do it because the stress is low. They do it even though what they do is unappreciate and misunderstood by so many people in the society. Now, maybe, you have found that low stress college, where teachers can waft in and out, meeting with students only on the lawns and dreaming wonderful ideas.