The standard argument is that some words with different meanings (and pronunciations!) can only be distinguished by ss/ß in writing, e.g. "Masse" (mass) vs. "Ma

The standard argument is that some words with different meanings (and pronunciations!) can only be distinguished by ss/ß in writing, e.g. "Masse" (mass) vs. "Maße" (measures). The first one has a short "a" sound, the second one has a long "a" sound.