While Android is vulnerable, especially to user stupidity, people mostly get scammed by fake credit card charges or by giving access to their notifications and contacts allowing for spam.
And yes, while there are "infected" APK's for popular apps , this again isn't the case here.
The real case here is money.
Apple earns $27B from commision on apps, while Google earns about $3B. Why?
Because Android users are "less willing to pay", which includes pirated APK's and "unlocked" app versions. Eliminating the possibility of using these for 99% of the people will be enough to force them to pay for that app/service in the end, raising the Play store revenues.
Do not trust Google when it comes to "doing it for the user" - their mission is to establish as strong of a monopoly on the platforms and extract as much value as possible. They spent more money on lawyers & policy lobbyists in the last 10 years trying to keep Android closed than some S&P500 companies are worth.