Auto-playing content really has no other purpose than to call your attention, even if that means irking the user.
Earlier Google offered an appetizer, allowing users to disable audio on a per-site basis. But now Google is doing it by default and auto playing content won’t auto play on Chrome 66.
Content that has no audio or mutes audio by default will still play automatically. If the site has been pinned to the Android home screen or a frequently played site, the content will play regardless.