For many years now we have had an annual policy. Family emergencies and holidays booked without any insurance in place have featured here on HT for many years. For some reason the fact something can (and often does) go wrong before the holiday never occurs to some people.
If you read the terms & Conditions of the Tour Operators you will see that you agree to take out insurance. In theory you can be asked when boarding for proof and turned away If you do not have it.
I have some sympathy for those who have a family emergency prior to a holiday and have delayed taking out insurance. Anyone going wthout is a fool.

Fiona you are quite right, Insurance should be purchased as soon as you have booked your holiday, you are at risk of cancellation before you go and without the insurance you will get nothing back.

I would like to think that most people know that they should have Travel Insurance but not everyone books with a Travel Company (I rarely do) so you do not have to agree to take out insurance when booking independently, though I have noticed that the budget airlines do offer the option of paying for insurance when booking flights. I know though that some people still think that an EHIC card will cover all of their needs which is not the case.

Having said that I have booked a holiday for July 2019, a safari in Namibia. I have a yearly Travel Insurance that covers illness whilst away but not cancellation, that is a separate insurance and because flights will not go on sale for another month I have no idea what the total price of my holiday will be and cancellation insurance costs are based on the price of the holiday. So at the moment I have broken my own rules of purchasing insurance immediately after booking a holiday. If for some reason I have to cancel during the next four weeks the I'll lose my deposit, a considerable amount.