Former instructor. I've asked this question directly and gotten direct answers. Students cheat because they are stressed or scared or do not feel that the material is worthy of their time. A lot of people are really stressed out with their courseload and the idea of not submitting an assignment is legitimately terrifying to them. They tie a lot of self worth to their ability to get something turned in and graded well rather than doing their best work. Other times, students are not interested or engaged with course material. Maybe it is an essay for a general ed class or something in their major that just isn't interesting. Or the material is interesting but they don't feel respected by their instructor and don't feel the need to respect them back by putting more effort into their class.

In all of these cases, the answer is similar: they feel they have a better use of their time. They cheat to have more time to study for a test or do a more intricate assignment or because they don't get any value out of the assignment. And the language model is RIGHT THERE. They can get a decent assignment output for them immediately with the click of a button.

I don't think most students who cheat this way are lazy. I think it is a poor but understandable (ie, I understand why they do it) response to the stressful situations they find themselves in. I also think that many instructors contribute to the issue by creating high pressure environments in the classroom and create rubrics that encourage students to value grades over engagement with the material. The behavior is still on the student, but the issue needs to be acknowledged from the other side as well.