A coworker asked me a few weeks ago why Christians have so many Bibles. I tried to explain to him that (in my case at least) they all serve a different purpose. Plenty of things come into play like the language (primary vs. translation); the base text (e.g., Byzantine vs. eclectic in the case of the NT); the translation philosophy (formal vs. functional vs. dynamic); the physical dimensions (e.g., hardcover vs. paper vs. leather; sewn binding vs. glued; wide-margin vs. regular; single vs. two column; etc.); the extraneous material (e.g., study notes; cross-references; articles); and a host of other things that could be mentioned.
Truth be told—we’d probably be able to get along just fine with one Bible—but why would we want to? If variety is the spice of life then why should folks who have the means live a bland existence? Plus, if we only had one Bible apiece then how would we ever be able to give any away to people who need them?!!