When I think of code, I think in mental models. I do not think in lines, spaces, indentation, and symbols—I think in variables, loops, and functions.
On higher-level, I think in modules, control flows, and data. Which are not visible in the code itself.
Structural Editors try to exploit this fact to build editors where you do not edit the source code (as in text), but rather operate on the abstractions.
This also explains why I remember code well.
Related to: Mental models make things easier to remember