My software is definitely not artistic expression. I signed over the rights to the software to my employer. These statements are not codependent in any way.
Copyright under US law does not require "artistic expression". One of the requirements is called "creativity", but it's very easy to meet. The key phrase is literally "some minimal degree of creativity".
The fundamental policy choice was to protect computer software under intellectual property law, with exclusive rights and market compensation. There were a number of ways that could have been done. Other jurisdictions toyed with new, software-specific laws. But in the end the call in the US was to bring it under existing copyright law with some tweaks to definitions and a small handful of software-specific rules.
A code in this sense is something different. It's a shorthand for a longer description of an object. It'd be like a hotel copyrighting the relationship between a room number and its physical location within the building, or copyrighting resistor colors.
In the US copyright just requires a level of originality. The bar isn't very high, but for example simple logos, like IBMs blue lines logo is not copyrightable.
There are examples of software code that is probably not copyrightable, but that's limited to very simple code that has only obvious implementations.
Our role as programmers being closer to artists than engineers does not make code closer to paintings than bridges. We do have highly repeatable patterns. Nearly every program can be essentially boiled down to some subset of CRUD + tranformation.
Even if it is art (I'm not convinced), the recent artificial scarcity on art is absurd. Some other thoughts to consider:
This isn't a counter argument, just pointing out how absurd copyright is.