WHY DO BABIES GET A VITAMIN K SHOT AT BIRTH?

How necessary is it? Is it compulsory?

According to UK NHS:

“Vitamin K is a substance that is naturally present in the body. It plays an important part in helping blood to clot. At birth, a baby has very low stores of Vitamin K and these are quickly used up over the first few days of life. This leaves the baby vulnerable to severe bleeding (haemorrhage) because they are less able to get their blood to clot. They may develop a condition called Haemorrhagic disease of the new born (HDN). HDN is a rare but serious, and sometimes fatal, bleeding disorder. HDN can occur up to six months of age, and can almost always be prevented by giving extra Vitamin K. NICE guidelines (1) recommend that all new born babies should be given a dose of Vitamin K to prevent HDN. However, it is your choice.”

I wondered why babies don’t have much Vit K in their bodies at birth.
When you know the potential sources of the vitamin, it seems obvious to me that any normal attentive mother will not be deficient during her pregnancy & should have an adequate supply if she is breastfeeding.
20 FOODS THAT ARE HIGH IN VIT K
https://www.healthline.com/nutrition/foods-high-in-vitamin-k

Perhaps the injection may be advisable if the baby won’t be breastfed?

Undoubtedly a reader may be better informed than me!