For exactly the same reasons you get it when abroad. Cancellations, weather, lost luggage, medical emergencies, disruptions, delays. Personal liability. Theft.
Ok we have the NHS for medical treatment itself but kids can get sick, bookings would have to be cancelled, and cottages/hotels can be expensive to just miss out on going when you’ve paid. if my appendix had burst in the UK I’d have needed specialist transportation home and that would have been expensive but covered.
If anyone has an underlying condition that there’s even a small chance could flare up. Just days before my appendix burst I was told by my paediatrician that it ‘would never burst’. Red faces there then.
We’ve got a couple of uk cottage breaks coming up, their policies state they can cancel and if this is short notice it’s would be hard to replace and we’d lose our other bookings based around it. Also got elderly relative I’m responsible for and small children so if anything happened there I’d have to cancel.