In reply to Charlie Merland.

Because in the past websites tend to crash on auto updates when plugins or themes where not ready to follow the changes WP made as they have and had a reputation of dropping functions/functionalities and add new ones instead without keeping the legacy code running. And nobody wants their site to go down. See what happened last year with one of the big changes in a Yoast Seo update. WP had a similar reputation. So developers started to turn off auto updates because of that.