Again, the purpose of the de minimus provision is to simplify record-keeping and tax reporting requirements. The government knew it was foregoing potential tax revenue by allowing businesses to keep these assets "off the books", but determined the compliance costs (to IRS and businesses) outweighed whatever tax revenue they are not going to get.
Keep in mind, you don't have to make the de minimus election; you can capitalize and depreciate any business asset you want to.
