Now, the internet is ubiquitous and many kids have access to connected devices at their homes (computers, landline phones) and it's harder to overview their use.
Also, the amount of content and extreme content available has exploded.
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I leave as an exercise for the reader to one-up this argument regarding the introduction of porn magazines themselves, porn drawings once paper became a commodity, as so on, dating all the way back to the first human sculpture (fat woman with giant boobs).