The critic Joseph Bédier (1864–1938) launched a particularly withering attack on stemmatics in 1928. He surveyed editions of medieval French texts that were produced with the stemmatic method, and found that textual critics tended overwhelmingly to produce trees divided into just two branches. He concluded that this outcome was unlikely to have occurred by chance, and that therefore, the method was tending to produce bipartite stemmas regardless of the actual history of the witnesses. He suspected that editors tended to favor trees with two branches, as this would maximize the opportunities for editorial judgment (as there would be no third branch to "break the tie" whenever the witnesses disagreed). He also noted that, for many works, more than one reasonable stemma could be postulated, suggesting that the method was not as rigorous or as scientific as its proponents had claimed.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): Why would editors only want two alternative branches when analyzing a text?
this would maximize the opportunities for editorial judgment