China building new coal plants (while also building new solar, wind, and nuclear) suggests that is not the only reason.
And it's not like any of the complaints about PV elsewhere are safety related.
> So sewage systems became popular before flushing toilets were widely adopted
What existed was not, however, sufficient. That is what necessitated building a massive new system:
"""The Great Stink was an event in Central London during July and August 1858 in which the hot weather exacerbated the smell of untreated human waste and industrial effluent that was present on the banks of the River Thames. The problem had been mounting for some years, with an ageing and inadequate sewer system that emptied directly into the Thames."""
"""During the early 19th century improvements had been undertaken in the supply of water to Londoners, and by 1858 many of the city's medieval wooden water pipes were being replaced with iron ones. This, combined with the introduction of flushing toilets and the rising of the city's population from just under one million to three million,[b] led to more water being flushed into the sewers, along with the associated effluent."""
"""The Building Act 1844 had ensured that all new buildings had to be connected to a sewer, not a cesspool, and the commission set about connecting cesspools to sewers, or removing them altogether."""
Just because a thing existed, doesn't mean they had previously done it at scale: the Ancient Greeks had electricity, railways, and steam; battery cars predate gasoline; we've today got the tech for a fully global power grid; none of this is at the scale relevant to the problems, and the same can be assumed for at least one possible thing that AI might force us to consider.
My guess would be spam and filters. Already exists, but likely to become so much more severe the old solutions will no longer hold.
Not that it really matters to my core point: what's the AI equivalent.
Spam and filters are a great example because spam filters are already AI. Literally neural networks trained to recognize spam.
LLMs are great at classification too so once they are small and cheap enough they could certainly be used as spam filters.
Also, you’re wrong about flushing toilets necessitating sewers. They were still manually emptying toilets in London when they built its sewage system. So sewage systems became popular before flushing toilets were widely adopted.