Unfortunately, FFS came in a time when sport/racing bikes were becoming leaner/more serious, shedding once wanted "convenience" items on their bikes like safety levers and side stands, because new riders want to approach cycling as a ore serious sport and the bicycles not "toys" as was the case for many people during the bike boom years of the 70's.
I think the FFS might have been more beneficial on town/utility bikes. Shimano kinda misread the market with their new invention in the late 70's/early 80's.