It's a great feature for people who know what they're doing, but you probably don't want all Android users to allow third party installs- it just opens people up to too much risk.
Amazon's been recommending + allowing it for years, along with every operating system for decades.
"your version of WhatsApp is outdated, please update to the current version", and after a countdown (or the click of a link), it downloads a malicious apk to your phone.
I'm completely disappointed, since too many websites use AdSense, and sometimes I can't even check a website, because the redirection is too aggressive.
I understand that the people behind these shady advertisements use aggressive cloaking (ex. only injecting the malicious redirection when you are under a mobile network) to avoid being discovered.
There are tons of malware that ask for shady permissions on Google's app store.. ala battery optimizer -- why Google expose people to such crap?