[gavinray]

Sure, but if one works, why wouldn't the rest?

It's like saying "we built a car engine, but every 33rd car we make the engine doesn't" work. That's not a very good engine.

Also, not sure why I am getting downvoted for saying I don't understand something and asking other people how it works.

[Redoubts]

Could you imagine more problems if you physically strung 33 cars together and tried to drive them in unison?

[gavinray]

Hmm, okay fair enough

[lamontcg]

Things like vibration and Pogo oscillation (https://en.wikipedia.org/wiki/Pogo_oscillation). All the engines collectively have about twice the thrust of a Saturn S-IC first stage (on the Saturn V rocket) and they're all going to be trying to shake the crap out of each other just due to thrust oscillations. If they hit a resonant frequency of the rocket it could shake the rocket apart. So, you can have 33 engines that all individually ignite properly on the pad and are all well-built to tolerances so that they function, but when you put the whole vehicle together and have all 33 of them pushing against the same airframe they could spectacularly fail.

[nvm0n2]

Yes but the reliability of modern car engines is a minor miracle, achieved through over a century of incredible engineering effort. Also remember that production lines always have yield, which means that not everything that rolls off it will actually work and the non-functional components are discarded. For example new chip production fabs very often have low yields, sometimes even the majority of chips don't work.