All human languages allow the expression of distinctions in time reference, so there's always a way to describe the situation that one event precedes another. Some languages do this with special grammaticalized markers, perhaps particles or morphemes attached to other words. Similarly: all languages allow the expression of the idea that a thing is small, or that it is big. Some languages do this with a grammaticalized marker – a diminutive or augmentative affix or noun class.
It is a basic property of languages that syntactic representations can have features of some sort, and that combinations of node can requirement "agreement" in those features. Very common examples are person, number, "gender" (including noun class and animacy-marking), definiteness, case, negation, tense). The general finding of linguistic typology is that in principle any semantic property can be grammaticalized and is subject to obligatory marking. However, some things are more prone to grammaticalization than others. Person and number are highly susceptible to grammaticalization, evidentiality is less-so.
Tense is more complicated because tense is traditionally used to indicate formal differences in verb morphology, but also to refer to precedence relations between events. A similar but different distinction is made between tense vs. aspect, which has to do with the "extent" of an event over time. Chinese does have grammatical markers for aspect.
The immediate explanation for why a given language mandates marking of some event-related property is that children learned that system based on the ambient data produced by their elders, who likewise learned a system from their grand-elders and so on. Most of the answer for a specific language is based on historical conservatism. There is a functional consideration that favors some system of marking, that there is functional utility to distinguishing between saying that some event has already happened, or is happening now, or is expected to happen (it's futile to try to prevent a fait accompli). Such communicative-functional considerations also favor the expression of number.