How come bit flips aren't destroying my computer?

https://stackoverflow.com/questions/2580933/cosmic-rays-what-is-the-probability-they-will-affect-a-program

The odds of CR-caused bit flips are discussed in the above SE thread, and as mentioned in this YCombinator thread linked in the comments above, the largest volume of data sensitive to bit flip (in memory) is media which won't have problems with this

In worst cases for the average person, the bit flip will result in an error which the system will catch and attempt to recover from. Now you have something else to blame BSODs on.

Besides hardening (like the hardware designs in spacefaring systems) and error correction (like the resilient architectures of SPARC CPUs or ECC memory), most current improvements appear to make consumer hardware MORE vulnerable to cosmic-ray-caused bit flip.

Because of this I think we can surmise that the primary reason your personal computer isn't riddled with errors is improved software design which is more resilient to small issues in the data.

That said, the primary lesson to take from this is that you have one more reason you should be backing your data up.