Surely the default position should be that children are in school during term, unless they are too unwell to attend or in exceptional circumstances? I don't think a week in disneyland is an exceptional circumstance. I think it is right head teachers can allow it is certain circumstances.
If you sign your child up to a school, then you are agreeing to abide by their rules (unless illegal, obviously). If you don't like the rules, send them to a school which rules you do like or home educate your children. You can't only abide by the rules you like and ignore those which you don't.
I can see the argument that poorer families cannot afford to go away during the school holidays due to higher cost at that time. I do have some sympathy, but also think that foreign holidays are not essential and education comes first. Not only that, but you can spend family time and "make memories" as many put it without going away. When I was little the only time away from home was going to visit my grandparents (at most once a year) as my parents couldn't afford other types of holidays until we were in our teens. Mostly we simply did days out or spent time as a family in the park/on walks with the dogs and so on. I have many happy memories of these times. You don't need to go away to have fun and have time as a family.
I was speaking to a good friend who is a teacher about this. Her view is that it does tend to depend on the circumstances. Attendance is one factor, others would be how the child is managing their current work and also the type of holiday/purpose of the absence. Sitting by a pool of a hotel complex or on the beach in the sun is lovely, but not always educational (I see many counterarguments that holidays can be "educational"- yes they can be, but how many actually are?
She feels that a big problem for some students can be that a new topic is started (and sometimes finished if they've been off for a few weeks) in the time the child was absent. The child then has to try and catch up what they've missed for the rest of it to make sense. For some children this is doable- especially if their parents help them catch up on what they've missed. But for some, it's much harder for the child and her. If a child is absent due to illness then it really can't be helped and you just need to get on with things. But it's not helpful for parents to take these children out of school unnecessarily. And it does create extra work for the teacher, which if a number of children in the class go off at different times can be a bit of a pain. I can absolutely see that if a number of parents take their children out at different times throughout the year it could be very disruptive.