Your native languages have an impact on -- and enrichen -- your worldview. The classic examples of this are inuits and amazonian tribes, which use (indeed, need) a few scores of variations of white and green to depict the subtleties of their environments.
It also structures the way you think in some sense, and can yield interesting subtleties in the way you express things and in literature. See how German, for instance, requires the verb to be put to the end of a sentence. With a long enough sentence, you can tickle the imagination prior to reveal what action all the beautiful words were applying to.
Lastly, there's more to it that simply having everyone speak the same language. A language can be very rich in vocabulary, and offer wide variations of vocabulary depending on the individual, and turn into a tower of Babel in its own right. English, in fact, is the best example here. A typical English speaker might know -- or at least commonly use -- something like 20-40k words; someone who speaks international English at a conversational level might typically know and use half of that. Contrast the two figures with the total number of words, which is well north of 500k in total: each specialty field and subculture has its own set of words.