I don't think that many motivated students can use the amount of time they spend on homework as a viable excuse for not getting involved in internships and community service. If you are motivated you will get done what you want to get done, homework and all.
I assume assignments help students achieve high scores in paper exams, but it is useless in enhancing students' capacity of using and applying theories.
Exams reflect a student's ability to use and apply the theories that they learn in class. It would not make sense for you to say that homework helps students get higher test scores but does not help them use and apply theories. They had to show what they learned on the test and homework is what helped them do that.
The steam inventor, James Watt did not attend school at his childhood also without chance to do any daily homework. People assume his success from his capacities of self-learning, theory-applying and operation activities. Unfortunately, for the students of day, most of them are busy doing their homework instead of something which may wake up their creativity.
I think the problem is that most students who do not get any value out of their homework assignments would not be doing anything "inventive" or "creative" in their spare time. The people who are productive with their spare time like that are the people who value their assignments because they challenge them to apply what they have learned in the classroom.
When you sit in a classroom and listen to the teacher talk you are getting input but no output. Without assignments the teacher would just lecture for days and days and then have a test at the end of every couple of weeks. That means that all that time the students would be unable to practice their essay writing skills or practice applying mathmatical theories and working out tough problems, etc. So when the test finally came and demanded that the students apply all of their knowledge, they would have no practice doing so and would most likely fail. This is an absurd learning strategy. If you believe in "studying" before a test, or practicing skills before you have to perform under pressure then how can you say that homework has no value?