> A company's codebase is a liability, not an asset
Its an asset. Like many (virtually all, other than pure financial) assets, it has associated expenses; maintenance, depreciation, and similar expenses are the norm for non-financial assets.
> Unless you happen to be one of the very rare companies that sells source code and not built artefacts, your asset is the built artefact and your code is the expense you take on to get it.
No, things that are instrumental to producing product are still assets, not just the things that you sell. That's true if its machines on your factory floor, if its the actual real estate of the factory, or vehicles that you use to deliver goods. And all of these assets, like a codebase, have associated expenses.
The whole "code is a liability, not an asset" line is something from people who might understand code, but definitely don't understand assets and liabilities.