Obligatorification

Following Jakobson 1959 [1972] and Lehmann 1982 [1995], grammaticalization for most observers always entails obligatorification. As Jakobson memorably put it, languages differ not in what they can say, but in what they must: [...]

Mandarin and Khmer and possibly other Southeast Asian languages may be characterized as resisting obligatorification of their meaningful morphology. Could this have anything to do with their penchant for decorative morphology?