The historian in me (can't beat the bloody idiot into submission, dammit
) wants to point out, too, that Valentine's hasn't "become" commercialized, it always was commercialized. Like all the other saints' days and holidays. Saints' days were excellent times for the Church to sell blessings, indulgences, and pardons (not to mention for everyone else to sell food, charms, relics, etc.). Major holidays - say the winter solstice/Christmas - were times to buy, buy, buy even back 1500+ years ago.
Which also applies to the question here . . . did the Germanic and Celtic tribes need
the winter solstice and its exchange of gifts (the root of our modern Christmas exchange) in order to display the bonds of quasi-feudal loyalty?
Well, no, they didn't. But it made a nice excuse to have a party in the middle of boring, depressing, despondent winter.