Every part on a bicycle is safety critical

I've had brake wires snap on me multiple times. On my old bike both brake handles broke (not simultaneously) rendering the brake in question broken. The chain coming loose is expected.

My latest experience is the handlebar rod breaking leaving the handlebar and the front wheel unjoined - I still have a 6x2 cm scar on my left forearm from this experience (road rash). I was NOT driving that fast, but taking a tumble with a bike can be eventful. I'm hopeful I will never experience losing a wheel while driving.

That's part of what makes bicycles the most efficient form of transportation: everything that isn't safety-critical has been removed.