Sure, if your CPU is controlling an airplane, it should better be redundant. Still, the CPUs inside your laptop, smartphone, or even compute server do their jobs pretty well without any error correction.
The transistors inside a digital CPU are of course analog devices. However, the digital interpretation of the logic levels means that analog errors do not propagate between gates. If the voltage fluctuations are small enough, the probability of triggering a logic gate incorrectly becomes astronomically small. Analog computers (such as all current quantum computers) do not have this feature. Each operation adds a little bit of error to the quantity that is being processed. This could be the voltage in an electronic analog computer, or the state coefficients in a quantum computer.
> Each operation adds a little bit of error to the quantity that is being processed. This could be the voltage in an electronic analog computer, or the state coefficients in a quantum computer.
This brings us back to the Quantum threshold theorem, which says that it's possible to design a quantum computer so that you can perform as many operations as you like without accumulating additional error, as long as individual gates in the quantum computer have a bounded amount of error.
This is one of the reasons why thinking of a quantum computer as "analog" will lead you astray. Quantum computers are more like classical digital computers than like analog computers.
The transistors inside a digital CPU are of course analog devices. However, the digital interpretation of the logic levels means that analog errors do not propagate between gates. If the voltage fluctuations are small enough, the probability of triggering a logic gate incorrectly becomes astronomically small. Analog computers (such as all current quantum computers) do not have this feature. Each operation adds a little bit of error to the quantity that is being processed. This could be the voltage in an electronic analog computer, or the state coefficients in a quantum computer.