There's tons of people over here taking 3 or 4 weeks contiguous, especially if they have children. That is in addition to other vacations around christmas etc. It's definitely not 5 separate weeks.
I don't think there's a lot of things that one could do in 5 weeks, but where 4 weeks would be too short.
Tons? Hyperbole? Are they teachers or something? That amount of leave in one go is basically unheard of, with the exception of maternity leave I don't know anyone who's been on leave for more than 3 weeks as a single block.
This is also taking from that same 5 week leave bucket people have available per annum, if they're taking 4 weeks then they have 5 days to last the remainder of the year. Not that crazy, but I have literally never even met a single person who does this let alone knowing tons.
I don't know if this is a Norway exclusive thing or if some other countries have similar laws aswell, but we have the right to take three continuous weeks of vacation during summer. You don't have to take the continuous weeks, but in my experience most people do