Why is aspect often more important than tense in Tibeto-Burman grammar?

In Tibeto-Burman grammar, aspect is considered the primary verbal category rather than tense because these languages are structured to encode notions like completed action, change of state, irrealis, inchoative (imminent action), and durative more readily than the temporal distinctions of past, present, and future.1

To express these abstract grammatical relationships, Tibeto-Burman languages often utilize a process of semantic bleaching, where full verbs—such as those meaning give, dwell, put, or finish—are specialized to serve as markers for verbal categories like causative, progressive, durative, and completive. Consequently, while some languages may utilize tense in specific contexts, such as split-ergative systems that distinguish between past and non-past, the fundamental grammatical focus remains on the nature and progression of the action itself.1