Families throughout Europe face the same sort of high costs for holidays outside school term time as those in the UK do but, up until recently, the UK was the only country which allowed parents to take their children away during school time. Thankfully we've now fallen into line with the rest of Europe.
My answer isn't based upon the fact that I'm well-known around here as a Europhile; it's based upon having had, as a teacher, to deal with the problems of kids missing important lessons.
If you're teaching a subject without a clear hierarchy of learning it might not be too difficult to cope with kids who've missed some previous lessons but it's an absolute nightmare if you're teaching hierarchical subjects (like Maths) because you need to know that your pupils understand what was taught last week if they're to be able to make any sense of what they'll be studying this week.
If the class teacher has to spend most of his/her time trying to assist pupils who've missed a week or two of lessons through term-time holidays that means that he/she has got less time to help pupils with full attendance records who might also be struggling to cope. i.e. OTHER PUPILS suffer if their classmates have just taken a holiday in school time