I think there needs to be a balance and be sensible.
When I lived in Australia, we planned to come back for the Jubilee and visit Europe. We didn't know at that point we would ever return to live in UK.
Whilst there was a one week term break, we took a further three weeks off from school. We had the blessing of the school as it was a once off opportunity.
Since DS was far far far ahead all the children in english and maths, there was nothing he was going to miss. If anything it gave the teacher a breather from constantly finding extra work. He was told to keep a diary - and he did - every day he wrote his diary and every day he worked out the cost of everything in Australian dollar. He probably learned far more on his holiday than in school.
It didn't do him any harm and he didn't mess anything crucial. But then, he gets a lot of support at home and we are very vigilant about his education.
I guess if parents aren't vigilant about education - then yes it is silly to take time off school to save a money or for a more convenient time. But if a parent is on top of it, then surely it is up to the parent.