1. It's very easy to visually check (five pairs of parallel lines) (by easy I don't just mean reliably, I also mean low effort, which is important because you do it a lot - point fingers at the pairs of parallel lines: "two four six eight ten"). It's very symmetric. If done wrong it tends to look radically different.
2. It requires pulling in 2 places in different directions to come undone. The bowline opens if you pull in 1 bad spot.
(3. In the gym, you can just leave the normal figure eight on the rope, which saves the next climber a bit of time. Not a lot, but it's a nice feature.)
Europeans sometimes do the double bowline (traced), but the naming is ambiguous in english, so you have to google double bowline on a bight.
Americans used to do yosemite bowlines, but that fell out of fashion because figure eight (safe and foolproof) and double bowline (safe, trivial to untie after hefty lead falls) cover literally every use case perfectly.
[0]: https://www.saferclimbing.org/en/blog/cross-loading-on-knots
[0] https://www.ukclimbing.com/articles/skills/how_to_tie_in_to_...
> IMPORTANT: This knot is methodically NOT recommended and yes, it MAY untie while you are climbing. It can happen if your rope is new-ish (and that means it slides easily) and if you don’t tighten the knot with a lot of force. I am always splashing chalk on the knot in case of new rope to increase the friction and I do tighten it with a lot of force. The reasonable and recommended alternative, pretty common and very safe is double bowline. It is almost as big as eight, but at least it is always easy to untie.
https://adamondra.com/updates/my-climbing-more-about-feeling...
Here is my pitch for "doppelter bulin" (double bowline on a bight):
Even if by some miracle the ENTIRE retraced half of that knot came undone, you would STILL be tied in with a normal bowline. I do a stopper knot too, but I think that illustrates just how bomber it is. And I only use it for single pitches for lead falls, on multipitches I still simply do a figure 8, because why get fancy?