I am sure that nutritionists _understand_ the popularity of sugary drinks, as in, they know what human motivations are, and they know why people prefer them to better foods.

But nutritionists also _understand_ that sugary drinks are bad in the long run, and that is why they keep saying that one should drink less of them, over and over. If at least few people get convinced, stop drinking sugary drinks, and avoid diabetes and heart disease, they nutritionists succeeded.

The same logic applies to blockchain/crypto-currency warnings that HN commenters produce.