As njarboe wrote, only recently, and it is by no means restricted to the West (see China or Soviet Russia). The only reason why it is shocking vis-a-vis the West is because it is a radical break with the ethical principles the West has acknowledged (and yes, often practiced poorly) for almost the last two millennia.

The most demented part of it is that as horrific as the practice was historically, as the article here shows, the reasons, as crazy as they were, were at least centered around existential and cosmic concerns. Today, we sacrifice out of inconvenience, or because we "made a mistake", and someone has to pay, but not the guilt party, of course. But because we are still influenced by those "old principles", most of us cannot even consciously face what we are doing. We dehumanize the victims through piss-poor pseudo-intellectual gymnastics so that it all computes in our psychotic calculus of moral purity.

Now compare the possibly hundreds of thousands the Aztecs sacrifices to the 60+ million sacrificed in the US alone since 1973.

So not only do we sacrifice at a far grander scale than ever before, we deny that we do so because we're too cowardly to look the truth in the face. We're not the Aztecs! We have the decency of performing our sacrifices discreetly, out of sight, by other names, and with a _sophisticated_ detachment. We're civilized, damn it!

Though I don't agree, I acknowledge this as likely the best counterargument to my point above.

Only very recently in Western Civilization has this been enshrined in law in most countries and is still a very highly contested issue in many.