Isn't that when the business majors took over?

There were ads on google.com since at least 2000[1]. Chrome wasn't announced until 2008. Disclosure: I work at Google but not on ads or Chrome.

[1] https://googlepress.blogspot.com/2000/10/google-launches-sel...

Ads are a paid transaction and Ad Companies absolutely need to be held liable for the money that they take because of who they take it from voluntarily. Google should be ashamed at all the money they are making from scammers and criminals and other evils. They should have a terrible score at every agency remotely like the Better Business Bureau. They should be tarred and feathered in public opinion. The brand name should already be tarnished by all this Evil across too many years of negligence. Same goes for Meta/Facebook, though they do have some of the tarnish already, more than Google has managed to get to stick. (I think too many people still want to believe the "Do No Evil" lie and its lasting brand propaganda.) Other companies should be wary of working with Google because of that bad reputation. ("No, we won't be using GCP because Google does too much business with criminals.")

Yes, it is hard to scale Terms of Service enforcement. Yes it is a hard problem to solve finding bad actors at scale. That shouldn't be a free pass to just not do it at all. Especially when money is changing hands. If someone is paying you to be a bad actor they are either paying you to look the other way (called a "bribe" in most jurisdictions, and illegal in some of them) or you aren't doing due diligence before accepting bad money (called things like "laundering" and "embezzlement" at scale). "It's hard to scale" doesn't sound like a good excuse to do financial crimes, last I checked with banking regulators and is in fact the opposite (a larger crime); why should Google or Meta get a free pass in advertising because they don't want to put the work in and take the revenue hit?

They don't. DMCA safe-harbor covers copyright violations. All it takes is a prosecutor willing to use the CFAA to hold business as accountable as people.

most people publishing a website either cannot or do not care to host the ad server on the same domain, they just want to monetize the site.

things could get a lot better, but this self hosting suggestion in particular will never see wide adoption unless major hosting providers build it and host for their customers. most people don't even bother to self-host/bundle stuff like their fonts and JS libraries unless they have have a JS framework in the loop doing it for them.

Modrinth’s ads are this way.