Google appears to either not screen ads at all or willingly allows misleading and lying ads and scams to reach its users. They profit off fraud by either laziness and ignorance or malice, by letting "ads" like "Your PDF reader needs an update" through. And they don't act on them when they are reported.
Every single company putting ads up in public is held to a higher standard.
All 5 daily users of Bing search were immediately notified of the exploit.
If you know (or are related to) anyone who is likely to click on scam links like these, do them a favour and install an adblocker on their browser. Upgrade them to a better browser if necessary. Don't just tell them they should do this. Sit down at their computer and do it for them. Ads have become a safety risk and that's not going to change anytime soon.