Once, people used their hands to write words, words that went on pieces of paper. To formally show gratitude, people would put words on a particularly nice piece of paper in the mail. You sent a thank-you note. Simple.
Now, not so much. Email is the standard of written communication and, in theory, an equally acceptable means of saying thanks — were it not for the Miss Manners of the world, who will occasionally remind us that, no, you still need to send a note. But on what occasions? For wedding gifts? Or any old dinner party? I send thank-you note, as opposed to an email, am I trying too hard? If I don't send a handwritten card, am I rude? And for the love of God, why must it be a handwritten note when I don't even need to hand-write my checks?
The issue of how to show gratitude, and whether the ritual of a thank-you note is something we should continue to adhere to, was recently addressed in T: Style mag, which notes that this seems to be, ahem, a girlish issue: "'It's just another bit of etiquette, the kind only assigned to women; what man is ever expected to write a note and send it?' […] Could it be that gratitude, like fat, is a feminist issue?"
Quite possibly; it's also an outgrowth of the difference between the social occasions associated with men and women. The special occasions that traditionally fall in the realm of female social life — bridal showers, baby showers, elaborate garden parties bursting with peonies — are a bit more rooted in old-school (and increasingly irrelevant) traditions and etiquette, far more so than is the case for men. Lucky us. But if we accept that men aren't expected to send a note, we should also acknowledge that they also probably don't expect to receive a note — an email or text message will probably be more than fine for most guys. So while The Thank You and how to go about it may be a feminist issue, nowadays it's more perpetuated by ourselves.
But how long this remains an issue may be a generational thing — in my experience, it's the older folks who notice the handwritten effort. Case in point: In college, a group of us took a road trip and crashed at a friend's home; I later sent his mom a thank-you note for letting us take over her basement. I didn't see her again until her son and I started dating, nine years later, and she remembered me as the nice girl who she met for 5 minutes once. But I'm not sure I would've sent the note if I was staying the night at a home belonging to someone under 40; somehow that feels "off," like I'd be trying too hard.
And then there's being the recipient of thanks, rather than the giver: When I knit a hat for a friend's newborn and failed to receive an OMG THANX UR SO TALENTED email for five or six days after it was the package was supposedly delivered, I freaked out (not at my friend, but at the idea that the hat — which was my first real knitting project and took a comical amount of time — was snatched from her suburban porch or something). Of course, her really sweet handwritten note arrived a few days later, and I felt like an asshole in that it didn't even occur to me that she was going the traditional route. But the days before the note arrived felt weird. Was the hat lost? Was my friend just overwhelmed with diapers? Where was the email?
Obviously no one dislikes getting a handwritten thank-you note. They're thoughtful and you have to appreciate the time that goes into them — and handwriting is practically a rarity these days (I can barely write out my full name anymore). But as the world moves ever-more quickly with increasing expectations of immediate interaction — email, text messages, instant message — it doesn't make much sense to hold on to the expectation of a long-held tradition. Especially when that tradition involves ten times more work, such as in cases of weddings and baby showers. If you know that the guest of honor has to send out dozens of notes, you might suspect that it's crushingly time-consuming. If you suspect (and probably not incorrectly) that the sender isn't thrilled about the implicit obligation of thank-you notes, doesn't it kind of ruin the effect of the note itself?
Related: Gratitude Adjustment [T:Style]