I think the argument is that it's possible for a kid browsing to, in a succession of clicks, go from (for example) a surfing website to something they really shouldn't be looking at. These clicks may be naive curiosity on the part of the kid, rather than intentional seeking.
Some of this porny drift would be encouraged by affiliate links and ads. Our society is broken in many ways - who could disagree? - and this tendency is one of them.
One of my burdens as a parent is to provide a counter to this porny drift, and to the other broken aspects of our society for that matter.
Lest anyone think this is pure hypothetical, this happened to me. When I was 6 or 7 years old, my parents let me have an account on the family computer. I couldn't do anything particularly destructive, and didn't spend an overt amount of time on it. Mostly, I would press random keyboard keys into the browser's URL bar.
One day, I ended up at a website that said 'must be 18 or over to access'.
(I suspect it was a credit card scam, not porn, but the point still stands.)
Next time I logged into that computer, I found myself unable to start the webbrowser.
One of the teachers in my wife's school was having the students research the government and asked them to find the address of the President of the United States. Well, most of them typed in "whitehouse.com", which at the time was a porn site. The teacher had to rush around the room turning off the monitors and dealing with the chaos. The site they should have visited was "whitehouse.gov" but they didn't know that. Something like 1.1.1.1 for Families would have prevented this from happening.
I work closely with the school and am keenly aware of the dangers of censorship. We do NOT want to block access to some things that sound like they could be "bad" (ie. Essex England, breast cancer, etc.) However, that doesn't mean its a free for all where you can go anywhere and see anything. The Internet is a really, really big place for a 1st grader.
Some of this porny drift would be encouraged by affiliate links and ads. Our society is broken in many ways - who could disagree? - and this tendency is one of them.
One of my burdens as a parent is to provide a counter to this porny drift, and to the other broken aspects of our society for that matter.