Depends on age, definitely. And the nature of homework seems to change too over the years.
What dd in Yr 7 is getting is mainly project type work which is spread over a period of time: it's to teach her time management as much as anything else.
She is old enough to understand that if she gambles on having oodles of time/feeling fit and well/the computer not going wrong during the weekend when a 4 week project is due in on Monday morning- then she has only herself to blame!
The day to day homework at this age is mainly things like learning vocab- you can do that in the dinner queue or in the car or wherever.
For a child in infants it is a different story. I would be quite lenient in Reception and Yr 1- dd was very tired at this age, and a lot of the time I didn't even bother to write notes. Or I wrote things like 'dd spent 10 minutes on this but found it difficult/was too tired to understand it'.
For ds who is in Yr 4, it's a sort of halfway house. If it was something expected coming up (most birthdays are IME) I would remind him of it earlier in the week and point out that he needed to get started earlier than usual. He rarely has homework that has to be completed from one day to another; they usually give it out a few days in advance and they have a set homework day for different subjects so, it's all very straigthforward. If things really got mixed up, I might write him a note. But it hasn't really been a problem: his pieces of homework are generally so short that I could get away by simply getting him out of bed half an hour earlier in the morning or letting him stay up for an extra half hour.
He has had lunchtime detention once for not completing his work (his own fault): I pointed out that this was not his teacher being mean and wanting to punish him, but simply because the work needed to be done at some stage, for the sake of his learning; if he hadn't done it before, he would have to do it at lunchtime.
I did feel homework more of a burden in infants, but that wasn't because dc's spent so much time actually doing any work: it was all the tedious time they spent fooling around. Now that they are a bit more business-like about it I am realising that the actual homework in these particular schools is not massive; it's not going to stop them from being rounded individuals.