It might be useful for merchant only in the case BTC price will go up and this will create an extra gain.
Merchants have everything to gain by accepting it while giving discounts as there's already a normal markup on most items. So, cut it enough for people to want to trade you their Bitcoin for products and the more this happens and these merchants keep even a small amount of their Bitcoin sales in house as time goes by, there's no way the Bitcoin doesn't appreciate. People are suckers for deals and most women have value savers tickets on their key chains for a reason.