Add to that predictable flat pricing. If most Wordpress sites became famous overnight I guarantee 90% of users would rather the site go down than figure out what to do with 15 minutes of fame and a 50k hosting bill
I maintain a few WP sites for small businesses. Precisely none of them would benefit from the kind of traffic spike that would incur a $50k cloud scaling bill.
If you’re running an online store, maybe, but by now almost all of those businesses are on Shopify where that isn’t an issue. 99% of all the businesses with WP installs I’ve touched would only be harmed by autoscaling instead of just choking on the traffic. Think local service businesses and restaurants.