Simon Bird opined "The thing I find interesting is that front clanger, rod or suicide derailleurs stayed in use on racing bikes for so long. Why was that? Surely their weight was greater and the cost of the Simplex and Huret gears wasn't so great...."
For racing bikes for regular cyclists and given their economic environment of wages, etc., I imagine that cost would be a significant decision factor in choosing between a cable operated front derailleur or a lever front derailleur. After purchase of a cable operated front derailleur, the cyclist has to purchase derailleur cable, derailleur cable housing, new downtube shifters or a left-only downtube shifter or a left handlebar-end shifter, and the necessary cable stops/guides. Compared to that, the lever front derailleur was a single item purchase, simple to set up, and shifts quite well. For racing bikes for well-sponsored racers, I imagine other factors than economics come into play.
Peter
Peter Brueggeman
La Jolla California USA
4peebee(at)peterbrueggeman.com