More than likely it's for the "tangible property tax". Here in FL where I'm at (no state income tax) counties can assess a tangible property tax on non-real estate property used for the production of income, each year that property is used in income production. Typically, the tax is a percentage of the FMV of the asset, which gets lower each passing year.
If using SEC179 you reduce the cost basis of the non-real estate asset to zero, that would mean they can't assess the tax after the first year. Therefore the reasoning for non-conformity to federal methods.
