The idea is, that there is some asset generated by the devs (software, etc.). Same as a machine that you buy and that generates revenue over time (and loses value over time). So the work result (the software) of a dev generates revenue over time and the costs are spread over time as well.
I guess I'm preaching to the choir here, but a machine has re-sale value outside of what it produces, which is what actually makes it a "asset". This argument could be applied to any knowledge worker that makes a spreadsheet since you can sell the spreadsheet.
You are actually pointing out the difference between physical assets and intangible assets. Mailing lists are the classic example of an intangible asset. Trademarks as well. For clarity, the argument is that a firm could sell the software developed by engineers if it wanted to
I'm not sure if I can follow your argument. A software dev usually works on something that is actually sellable (the spreadsheet software itself or a SaaS platform). If we take Facebook the platform as an example, for sure you could sell the software. Or a startup like Windsurf that gets bought because of the software they developed. So from my perspective devs actually create assets.
If there should be tax discounts to make it attractive to develop software is the political decision.