Because in Chinese we don't embody tenses by using different forms of verbs. In other words, we don't care tenses much in Chinese, that's why tenses are a big problem to Chinese when they learn Indo-European & Latin language, I met lots of westerners who thought Chinese was crazy without tenses, and I told them Chinese thought your languages were more complicated with tenses. And in fact we can express the future tense not only by 将. Let alone those 'symbol characters' of the tense like 要，会，去，actually most time we embody the future tense without any 'symol'.

你“会”来中国吗？ 你“将”到哪里？ 他“想”去北方念书。 她“要”的是什么？ A 小明要“去”他外婆家，这个周六。B 啊！我以为他已经去了