One of the techniques used by statists to control what adults can read and see is to pretend that it's all "for the sake of the children". We are told that we must censor books, movies, music, television, etc. to "protect the children". But censorship attempts in most of these media until recently when a different technique started to be used (nominally private companies like
Google, Facebook, Youtube, and most especially
Twitter imposing censorship at the behest of the federal government) never got very far because it was generally understood that the federal government had no authority to censor anything except what was sent through the U.S. mails and because these were recognized as
adult media. State censorship is a different matter, but at least the courts have up until now imposed some limits (although not enough) on what may be censored by state authorities.
The problem with comics in America as opposed to, say, Europe and Japan, is that comics here have always been considered a children's medium, and that was even more true in the 1950s than it is today. That left the medium open to attack on the grounds that it was harmful to children, and such attacks began around 1947 by Dr. Fredric Wertham and others. To be honest, pre-Code horror comics with their incredible amounts of blood and gore were reprehensible in my view, but I doubt very much they were responsible for turning children into juvenile delinquents. They were the principle object of Wertham's rage (and to him, even superhero comics were "horror comics"), but he had a secondary target, and that was sex.
We don't need to go into every aspect of sex Wertham found objectionable - he hated "headlight" comics in which women were drawn with prominent "headlights" as some boys called them (one wonders if he thought every woman should be drawn with an AA-cup sized bosom) - but unfortunately for us, he specifically mentioned spanking in his notorious
Seduction of the Innocent, referring to it as "sexual flagellation upon the buttocks". Comics were, then, under fire, with a Senate sub-committee even holding hearings, and despite Congress having no authority to censor them, the publishers, who were for the most part a disreputable and cowardly bunch, feared government censorship and decided to head off that possibility by censoring themselves with the Comics Code Authority in 1954.
For the first two years, the spankings continued, but once
Mrs. Guy Percy Trulock and her "Code Ladies" took charge in 1956 they apparently took Wertham's "sexual flagellation upon the buttocks" very seriously, and I believe there was only one non-parental, non-robot adult M/F spanking during the following decade (in
Career Girl Romances #45). About two years ago, I went through something like 600 romance comics from the "dead decade" and came up with no spankings! And notice that this week's Nancy/Hedy spanking, which isn't even M/F, took place in 1956 just before the "dead decade" really went into effect, and there were no spankings in
Patsy Walker after that. It wasn't until 1966 that the dam was broken and the spankings resumed, and not until 2011 that the Code was finally laid to rest.
Believe it or not, Butch, that's the short version.

If you're interested in more details, I go on at even greater length in
Frontier Romances #1 and my article
Effects of the Comics Code on Spanking, Part 3.