Remember that the widths of the oxide tracks within the silicon is on average 40nm these days (that's only ~400 atoms across!) or even smaller. with hundreds of process steps. One big molecule from some tiny error in the production process on the wrong part of the chip may not cripple it, but may impede performance, it's just probability at the end of the day.
With regards to potential fails going into production, it does happen, there are several test phases during production to catch as many as you can, but at the end of the day you won't get them all.
Semiconductor fabrication is fantastically expensive, new Fab plants cost several billion to build, so if you want to guarantee quality you have to pay for it.
It seems like a really good idea. It also seems like it must be pretty hard to do in a way that gives you a reliable (say) 10% emerging as 'lucky.'
You design those percentage bands, generally to the size of the market you're aiming the chip tiers at. The silicon will be as good as they can get it generally, nobody wants to push bad products out. Recalls and returns probably cost more in the long term than failing more chips and suffering a worse yield.
However if only 0.5% of your customer base is interested in paying more money for a faster chip, you only cream off the top 0.5% of chips.
Clever little hardware hacks gives you oodles of geek street cred, but it may mean putting up with occasional bizarre behavior so that cred is well-earned. When silicon fails, the apparent effects can defy all logic. We can be talking about a logical AND that does something else entirely <0.001% of the time.