Students do not have equal resources for completing homework. (computer or internet, time, study space, privacy etc…)
Homework that is busy work is often copied just for completion.
If homework is summative then it must be graded. Often homework is merely checked off.
Student homework assignments are the most likely to receive zeroes which can negatively skew the total grade that may be indicated by summative assessments.
Homework should never be assigned over holidays thereby interfering with family plans. Kids do need a break.
Many students have nights with hours of homework. Could students more out of 15 or 20 minutes of well planned practice rather than an hour of busy work?
If homework is based on course standards then not doing the homework should naturally affect their grades on summative assessments. For this reason no separate grade should be necessary.
Zeroes in homework followed by zeroes on summative assessments is punishing the student twice for that content.
Failure to complete homework is a responsibility issue, and, as such, should be treated just as inattentiveness, not bringing materials, disruptiveness and similar issues.
Many home help sites have blossomed in the past decade, casting doubt on how much work the student is actually completing.