It breaks more often than it doesn’t. Yes, the page “scrolls”, but it scrolls only a few pixels, while the internal “custom” scrolling implementation doesn’t respond to the event and does not scroll to top, resulting in a terrible UX.

When you scroll on reddit, there is a beginning and no end.

Some applications have neither a beginning nor an end, so scrolling to the beginning makes no sense. At best, you could make "scroll to the beginning" get back to the start of your navigation, but then your scrollbar wouldn't let you go further.

(also if you have both horizontal and vertical scrolling, you're still left with no horizontal options)