I'm not sure appealing to a walled garden is the right approach here? This is, of course, why there are no explicit pornographic apps on the Apple App Store. They've explicitly forbidden it (section 1.1.4 of the App Store Review Guidelines: https://developer.apple.com/app-store/review/guidelines/).

You're basically trading one regulatory body for another. Perhaps Google makes the "right" decision now, but you disagree with their SEO metrics in the future? We are already beholden to undemocratic tech platforms for a lot of our life, why provide them even more power over our lives? I realize that sounds a little hyperbolic, but it's interesting to see that we are much more comfortable with a multinational corporation that doesn't even have a customer service department to make rules about the Internet rather than a democratically elected government.

Google doesn't publish statistics AFAIK about adult search terms, but evidence from several sources puts adult related search terms at around 10-15% of search volume. Given our metric-obsessed micro-optimization culture, if even a small proportion of those users decided to shift to DuckDuckGo or Bing because they suddenly couldn't search for porn on Google, that would have a material effect on their advertising and bottom line.