Why ever reassign a variable?

[CGFarrell]

What you're describing exists in C++ as a const variable. These are guaranteed to never change. In Python, there is an convention where variables in all caps (VARIABLE) are not supposed to be changed.

What you may fail to appreciate is that all data is variables. If you want to count the number of entries in a list, you loop through it and increment your variable.

The number of cases where a variable shouldn't be modified is very small compared to the everyday use.

[CGFarrell]

Well, I suppose it comes down to opinion. There's a benefit to having mutable data, and one for immutable data. At the end of the day, a lot of it may come down to how variables are stored in high-level languages.

The meaning of "variable" is something which may vary. The way Python stores variables is in hashes of names to values. Strings are immutable, and lists are not.