If you don’t point to the knot on your harness when calling out that you are tied in, and we don’t audibly call out “On belay... belay on” to each other, we aren’t climbing together.
These exact same rituals have been developed for climbing because everyone, experienced, and inexperienced, can make mistakes.
The greatest climber of her generation (of any gender!), Lynn Hill, opens her autobiography with the story of how she was distracted while tying in, and nobody thought to check her, because, well, she’s LYNN HILL.
She climbed 75’ up an easy (for her) warmup climb, called for tension on the rope, sat back, and fell the entire distance to the ground. She was very lucky to survive.