Not everyone has the luxury of being able to get leave during the school summer holidays, for example, tourism workers, hospitality staff, healthcare workers ... so of course their children don't deserve a holiday
Then there is the issue that sometimes family members are abroad and you need some additional holiday time to attend family weddings, grandparents' big birthdays, etc etc But often there is very little overlap between different countries' school holidays. But I guess these children don't deserve holidays to spend time with family either
Then of course holidays are only for the wealthy as everyone seems to remember the days where you could rent a cottage for sixpence - totally ignoring the fact that even what we remember as "cheap" holidays - camping, self catering etc - can cost in the £1000s these days.
Then of course there are the environmental arguments that I have read. Of course the irony is, that if you don't fly and instead use car, ferries, trains etc to travel 1000-2000 miles to your holiday destination, then it takes much longer and you need more time out of school ....
It all makes me happy that my children went to school abroad where the system is less rigid and draconian and children are allowed to take up to 10 days of authorised absence so they could attend family weddings, their Grandmother's 80th birthday, have holidays with family and go away even when leave was restricted so they did not have to spend the entire year in school and childcare.