There is also a theory that soft and inelastic noodles have come to be used exclusively, because cooks noticed that such noodles mixed easier with soup broth than elastic noodles, when Udon noodles were served with warm soup broth.
温かい汁でうどんを食べる場合、強い腰がある麺よりも腰が弱めで柔らかい麺の方が汁と絡み易くなることに気付き主流になっていった