I think there are an awful lot of responses that seem to assume it is just about the money - its not!
Many people working in factories have official 'shut down' periods when they have to take their holidays. The factories decide when these holidays are, and in my brother's factory, almost all the holidays are in term times. Men working in these factories have a choice: term time holiday or no holiday with their children. It was the same for my father and the (different) factory he worked in. His shutdown was the first two weeks of July - so if we wanted a holiday, we had to have it in term time.
Further, other people have to 'share out' the holidays between the staff. I know in my husband's department they are only allowed one member off on holiday at any one time. Now I'm not a maths teacher, but I know it is impossible for all the staff where he works to take time off in school holidays.
Also, some companies have busy times when they ban time off for staff. My husband is not allowed any time off in August, my friend works for an exam board is not allowed any time off between the exams happening in May / June and the results coming out in August! When do these people have holidays??
To just say everyone should stick to term time holidays is incredibly naive and does not recognise the fact that people often live very complicated and difficult lives these days, and we can't all just rock up and demand time off during the 12 weeks school holidays. Bosses and workplaces just do not accept that anymore. Therefore, there needs to be a degree of flexibility.
I also think the government needs to stop hiding behind the red herring of pretending that holidays are the problem. I'm a teacher (and I take holidays in term time too - I have different holidays to my children - different LEAs), and I know the good kids who work hard all year but take a week's holiday are not the problem. To think that they are is missing the point and is a massive failure on the government's side. They need to crack down on those students for whom attendance is a real problem - and that is those students who do not like friday afternoons, wednesday mornings or whatever. To focus on holidays when real truancy problems are not being dealt with properly, is a crying shame. (This is both my experience and my opinion!)