I do understand that families need time together without the normal stresses of day to day life and that the only way some families can afford some kind of break of that nature is to go during term time. I also understand that there are parents who cannot get time off during the school holidays so need to request taking their children out of school during term time.
But, I think the majority of the people who are taking their children out of school during term time are doing so to get a better holiday than they could afford during school holidays.
Someone above mentions CentreParcs and the difference in price between going in term time or holidays. well, we're a family who cannot (would not!) pay £1600 to stay at Centre Parcs for 4 nights during school holidays. So we just don't go! It's not madatory. We'd rent a cottage or look to go to Centre Parcs or an equivalent in Europe when we have school holidays and their country doesn't.
Two years ago we went to Croatia for a week for £750 (that's flights and accommodation) for a family of four. In summer school holidays. Last year we went to France and were able to book a 2 bed cottage for £400 and we took the cheap ferry crossing from Dover to Bologne for less than £100 in school holidays and accepted a longer drive. I'm not even going to pretend they were educational. We spent most of the time on the beach knowing that happy children gives us a break!
Other years we've just not had a holiday or we've camped, or we've booked a last minute cottage for October half term. We've even stayed in a grotty caravan park in Suffolk but we just used it as a cheap accommodation base and had day trips out and about. We're now getting to the point where the children are old enough to appreciate being taken further afield so we're camping this year and saving up for a bigger trip for summer 2012.
So I have every sympathy for those who genuinely cannot afford any break away with their family unless they go during school holidays and would expect the school to use their discretion and authorise those absences but as this thread has shown, most people expect a certain type of holiday and use the term time dates to get a better holiday.
When you don't permit yourself to take children out of school during term time or aren't able to do so because you work in a school, then you never have that 'better' expectation, you just look for the best you can afford during the school hols.