Normally when a business spends money producing a valuable asset, it is required to depreciate the cost to acquire the asset over the useful life. If a business pays people to create a new building, that is depreciated over 20 years. Even if it was paid for as salaries of employees, it isn't a special situation unique to software engineering.
I don't think that's quite right? The value of the asset itself is depreciated over years, sure, but the payroll itself for the employees is just an immediate expense.
But isn't the reasoning there that you could turn around and sell that building right away?
The reasoning behind depreciation is matching the income produced by the valuable asset, not really about resale value.
Presumably the value for tax purposes is based on the cost because the cost is harder to manipulate for something like software. Like some big box stores argue under the "dark store" theory they should be valued for much less because they have restrictive covenants banning competitors from using the property if sold, or that vacant property should be used as comparables.