My derailleur geared bikes all have 7 speed cassettes. The spacing on 7 and 8 speed cassettes is wider between cogs than on 9 or 10 speed cassettes. This makes it easier to use either an index or friction shifting system, because the shifts don't need to be as precise. Two of my bikes have Shimano bar end shifters for the rear derailleur which can be used in index or friction mode. I set them as index most of the time, and the only time I make derailleur adjustments is when I replace the shift cable every few years. The index bar ends can be changed to friction with a twist of a round lever on the shifter.
My front derailleur shifters are friction. On a triple chainring, the large and small rings are effectively indexed anyway by the "stops". All that leaves is the middle chainring, which is roughly in the middle position of the bar end or downtube friction lever rotation. I don't get the point of an "indexed" front shifter, they are actually worse because you can't make slight adjustments that are sometimes needed due to the chain angle. I make one front shift for every 8 or 10 rear shifts, so I still have a 25+ year old friction front downtube lever on my 1980 Ciocc road bike. They will outlast most bikes.