Seeing a statement like x = x + 1 is perfectly normal in standard software development, but it creates unnecessary complications for a prover. When variables change, the prover is forced to continuously figure out exactly which version of x is being referenced at any given point in the code. Thanks to LLZK, this problem is completely avoided because every single value is assigned only one time. For a deeper understanding of how this single assignment approach streamlines the verification of ZK circuits, you can read the breakdown provided by @RaghavMalik15.