The step up in basis also avoids a logistical nightmare, as it can be extremely difficult to determine the cost basis of an asset owned by someone who is now deceased.
If we're not taking in enough from inheritances, we should change how the estate tax works, but eliminating the step up in basis generally would just result in a substantial increase in administrative overheads.
Finally, to the extent that there is a problem with gains totally escaping taxation (e.g. via trusts)-- the article doesn't use any of its massive felony private violation to make a case for that.