> Think a factory or a mine. That may last for 20 years, but require workers to operate, maintain, etc.

Before Sec 174, s/w development costs were subject to a choice: amortization as if they were a capital expense, or regular deduction as a normal operating expense. Companies could decide which category to put costs into depending on the nature of the work (and presumably to suit their own interests).

Sec 174 removes that option. Or rather, it narrows it significantly. You must be absolutely confident that you paid developer X for ONLY maintainance work before deducting their salary.