Light bulbs burn out, so we make them replaceable. You don't have to buy a whole new refrigerator or light fixture just because the bulb is out. It's called failing gracefully.
Cars used to have two brake lights. In 1986, the law changed to require a third brake light, which makes the brakes more visible and also gives you two working lights if one is out. Very graceful.
Brake lights have two elements in them - one for when the brakes are engaged and the other slightly dimmer one when you have your lights on at night. Most bulbs either only have one way they can be inserted or the connectors are such that however you have inserted it, it makes the appropriate connection.
My car has a brake light that has two ways it can be popped in. Depending on which way you put it in, you have a 50/50 chance that you have it backwards and one of the two lights doesn't light up. The brake light will engage, but the other one will not.
This design had to get through both the engineer that built it and the QA personnel who double checked it to ensure it would function properly. You're telling me none of the QA team ever popped the light in the wrong way and was surprised that it didn't work properly?
Obviously it was caught at some point. The real question is who didn't care so much that they approved that design when a slight rotation of one of the guide tabs would make it so it only goes in the correct way?
What do we do with our customers, students, coworkers, or others we work with that creates a similar problem that a tiny one time adjustment would fix forever? What were we too busy doing that prevented us from making that change?