I believe that the question is asking about potential disadvantages to assigning students a worksheet for homework.
One possible disadvantage is that the worksheet is likely asking only questions that the worksheet creator considers important. A student might have a really creative idea or interpretation for a concept, but the worksheet might not ask about that part; therefore, the student never gets to voice his or her unique viewpoint.
Another disadvantage is that worksheets are often very objective in nature. That's great for the repetitive drilling of concepts, but it doesn't often (if ever) require higher levels of thinking on the part of the student.
One thing that I don't like about pre-made worksheets is that they don't always ask a question in a way that makes sense to students. Students will ask for clarification, and I will reword the question so it reflects the way I taught something. Generally, the student then asks, "Why didn't the question just ask it that way then?" Making my own worksheets would eliminate this issue, but creating all of my own worksheets would be an incredibly time-intensive process, and is not realistically possible.
One more disadvantage of worksheets is that they are frequently lost. This may sound a bit absurd, but I'm basing it on thirteen years of teaching experience. Whether intentionally fed to the dog or not, there is always a small percentage of worksheets that have to get redistributed because a student can't find the worksheet. Those copies add up over the course of the school year. Multiply that across dozens of teachers on campus, and there is an increased cost of paper that the school must pay. Some schools even place annual limits on the number of copies a teacher is allowed to make. If the teacher wants more, that teacher has to pay for it.