There have been multiple postings, including some recent ones, where problems that (according to their posters) are "practice problems" for a class, or from an exam preparation sheet are tagged by other users as [homework]. This means that if the posters of the problems are students, their grades are independent of how much or how little answer they receive for the questions posted to math.SE, because no reward or punishment is associated with submitting solutions of the problems.
In some education systems this is, especially at university level, the default meaning of "homework": grades are based on examinations, and homework is a suggested list of problems, not the basis of any marking of pupils. In some places not only is the homework optional, but students would be considered fortunate to have anyone read or evaluate their solutions to any of the suggested problems; it is not a feature provided by enrollment in a class or school.
I think the tagging as [homework] and the concern over the "problem" of homework is largely based on assumptions that the posters of questions stand to derive direct personal benefit (elevated grades) from a solution and might cynically solicit such benefit at the expense of users who answer the questions.
Given this, it should be clarified by those who consider [homework] an important matter for the site, whether the [homework] tag is intended for any problems in any way associated with schoolwork, or only for questions that are gradable.
Of course, the intention could be ambiguous or lacking in consensus. If so, it points to the need for more specific information than a question being [homework] or [not-homework], such as what level of answer is sought, whether it is a hint-request or solution-request, and the poster's background level. These are poster-dependent metadata that have a life of their own separate from the mathematical Q&A.