After my bar mitzvah, my mom z”l made me write 10 thank you cards a night until I finished.
After I got married, my wife and I wrote 5 thank you cards each, 6 nights a week, until we finished.
After my dad z”l died, my sister and I wrote thank you notes for those that sent meals, made donations, etc. The same after my mom died.
Writing a thank you is simply common courtesy, and unfortunately, it’s dying out. Moreover, it’s also an acknowledgement of a gift that might have been shipped and not given in person. If I arrange to send a gift, how will I know it got to the correct destination? How will I know it was appreciated?
I haven’t gotten a thank you card for any wedding gift we’ve given in years.