Why is that? If you don't have enough self-control to not use Reddit, a login wall won't stop you.
On mobile, when I tap reddit search results I am never logged in which means I have to go to old.reddit.com to see the full thread and comments. If they added a log in wall I'd just stop tapping reddit results on mobile.
You're not meant to take a proverb and apply it literally in all cases. It's a piece of wisdom you pull out when you deem it appropriate. The analysis and individual judgement of the human being is implied.
If you included more it wouldn't be a proverb.