Did your high school not have any kind of summative homework?

In many places, particularly in the U.S., there are few invigilated exams, and quite a lot of your overall grade will be comprised of coursework. This, combined with the inexorable advance of digitalisation of education has led to where we are now.

Certainly once you get to university level, there are projects which simply take too long to be done in the classroom, such as a dissertation or final report. These projects have always been vulnerable to commissioning rather than plagiarism, and you’d be appalled to realise how common it actually is even in higher prestige places. LLMs have simply lowered that bar to make it even more common.

This is a genuine problem, and people are more sophisticated cheaters than you might initially think.