I think maybe it is the idea that it is "work" they are doing and therefore a "chore" can be a problem.
My dd's do "Braintastic" maths and english on the computer which includes games so they don't really see it as "work", just fun!
Today we will be looking at a David Attenborourgh book on animals then finding out where they live on the globe, we can talk about geography and climate and habitats, they don't think they are doing 'work', we're just doing stuff together.
In this months EO magazine there is an article which answers just your question, and it talks about how school just 'turns off' children's love of learning.
I don't think endless 'worksheets' help enthrall kids very much.
Also we don't really do "a full weeks work at home",
so much can be achieved in a small amount of time because it's one to one, my dd has my undivided attention, we might be distracted by going off on a tangent sometimes, but if she doesn't 'get' something I try approaching it from another angle or just leaving it to another day.
We might have a week where absolutely nothing educational seems to have been done, and another week where we do loads, there are no targets or tests to pass or even anyone to compare her to.
Occaisionally I do worry that we are not 'doing enough' but when I look back over the past two years and look at the stuff my dds peers are doing in school I know I've absolutely nothing to worry about.
Most importantly I'm in control of my dds education and I'm not entrusting it to someone else, which feels very assuring.