1PW wrote:
If we take a look down the aisles of today's hardware stores,
metric is not easy to find.

Although if you look in a supermarket, almost every container is dual
marked with metric and non-metric units on the label. Unfortunately,
voluntary metrication (i.e. metric-only labels) is illegal. One of
several laws forbidding voluntary metrication in the US is the FPLA at
http://www.ftc.gov/os/statutes/fpla/outline.html.

There is a lobby (including global companies like Proctor&Gamble who
sell soap powder) trying to get such laws changed so that they can
reduce the costs of repackaging or relabeling. For them, the laws
forbidding voluntary metrication are a technical barrier to trade.