You can get by with just one (or one pair). But once you open the door to having more than one, you can end up with twenty and still find situations for which nothing you have is quite right, and a new purchase is required.
Guitarists with GAS (Guitar Acquisition Syndrome, per my father who’s got it bad) must always strive to make peace with the fact that they will never have enough guitars, and simply enjoy both the process of researching new guitars and the music they make with the ones they’ve got. And if you’re in the unenviable position of being the parent or a spouse of an individual with GAS, just take the same approach that you would buying shoes for a seven-year-old boy: at first just get something that fits the vast majority of situations, knowing that no matter what you get, it will quickly be outgrown, worn out, or otherwise outmoded.
Wearing Nikes in church = playing “Sweet Child o’ Mine” on a $100 Washburn acoustic. Don’t worry, your birthday is coming.