Got used to riding 2x5 and 2x6 bikes for many years and never really felt that I was deprived by not having enough gears. Usually stayed in the large front ring, so the small ring just provided a couple low bail-out gears for climbs. With the increased number of rear cogs and a wide-range rear derailleur one can get the same range of gears with only a single shifter and eliminate issues such as rubbing or adjusting the front cage. So I can understand the appeal although none of my bikes are set up as 1xN.