However, when some colleagues tried homework as 0% for introductory courses, most students omitted the homework, then failed the exams. Modern students seem to require explicit incentive to work, otherwise the usual: scrolling upon flat screen devices, hedonism, and so forth.
In this case, who has failed: the student, or the professor?
And to pass an exam students have to prepare for the exam. Homework will only help there if it is similar to the exam.
One time I had to evaluate a written exam where the professor had set up a trap. There was a question that looked like a standard question from homework, but if you used the standard-techniques from the course your calculations didn't work - it was a nasty special case. Most people that started with that question just burned 30 minutes without getting anywhere... a lot of students failed, but at least they learned something about life...
And Oral exams are different. Giving a quick well prepared answer and being able to solve difficult tasks over a few days are completely different skills. Students there prepare for the professor. There are transcripts of previous oral exams. And professors change over the years - the final tough question of an excellent student will a few years later become a starting question. People that didn't know that game and didn't have access to any transcripts were in serious trouble... None of the Homework would have helped in the oral exam.
And to pass an exam students have to prepare for the exam. Homework will only help there if it is similar to the exam."
That's not learning really. I can confidently say that because I was the one who unfortunately regressed to this during the uni, and the same story with my peers. One simply can't prepare to the multiple exams sufficiently in a few weeks time (or less). So the only path left is hysterical rote memorization of as much material as possible to squeeze in at a passing grade, and then immediately forget all of the materials in a few months time. Burst of "learning" twice a year for a short time doesn't translate into real learning.
And that's for some simple courses during first few years. Specialist courses later in the program sometimes are impossible to rush "learn". When I tried to pull this off for Probability Theory course, I've failed spectacularly to get even lowest passing mark at first try. And others failed the same way.
If good results are important, it's most important to know what happens in the exam - and adapt professionally. Learning is fun. I myself always did a lot of homework. But I wish I had been more professional - constant challenges are fun, but most of it is not very time-efficient.