Another important factor gets back to our Byzantine princess and her deadly sins: pride and vanity. As the wealthy began using forks, the started having them made out of precious metals and materials. Forks, like other objects, increasingly became vehicles for conspicuous consumption. And once that happens, everyone has to have them.
In the 18th century, people figured out that curving the fork and adding tines could make it easier to use on elusive foods like peas and beans. Meanwhile, the rise of forks meant the decline of knives. Louis XIV made sharply pointed knives illegal, presumably to curb violence (he might have been a little paranoid after the nobility revolted against him) and the new rounded table knives, fashionable everywhere as soon as they appeared at the French court, were totally useless when it came to spearing food.
By the 19th century, industrialization and the rise of the middle class meant that forks were no longer limited to an aristocratic elite. Now everyone could have their own flatware — and enough to offer their guests matching sets at dinner parties. Two-tined forks were no longer in vogue; now forks had anywhere from three to six tines — unless you were in America or a similar backwater. When Charles Dickens toured the U.S. in 1842, he noted that even the most polite Americans were still eating with knives and two-tined forks. But European civility was in vogue, and so the fork soon became standardized as the most important piece of flatware.
In fact, the Victorians found it so important that they invented scores of different kinds of forks — Victorian tables groaned under the abundance of unnecessary flatware, a different fork for nearly every kind of food! With our current cultural (and economic?) preference for casual dining, most of these have gone the way of the two-tined fork, but next time you pull meat out of a lobster claw with a tiny fork, you can thank the Victorians for their ingenuity!
So in tracing the history of the fork, we can trace the different Western attitudes toward cleanliness (Bad! No, good!), towards delicacy (Pretentious! No, civilized!), and towards conspicuous consumption (Ungodly! No, pretty great!). We can also see some general trends of material culture across the last millennium, especially the leap from virtuosic, expensive, one-of-a-kind pieces on royal tabletops in the Renaissance, to mass-produced quantity-over-quality pieces that emulate those European royals by the 19th century. Will you ever look at a fork the same way again?