It tends to be geographic, so if you live in a region that’s able to deal with lactose, you’d have the impression lactose intolerance isn’t super common. But entire regions are lactose intolerant, like Southeast Asia (including China) and about half of India.
Basically anytime you see dairy as rare or non-existent in a region’s traditional cuisine, that’s why.
It tends to be geographic, so if you live in a region that’s able to deal with lactose, you’d have the impression lactose intolerance isn’t super common. But entire regions are lactose intolerant, like Southeast Asia (including China) and about half of India.
Basically anytime you see dairy as rare or non-existent in a region’s traditional cuisine, that’s why.