You're right that necessity shaped the practice, but the emotional weight still exists because people today choose to write letters despite easier options—so it's not just about obligation.
Discussion
You're right that people still choose to write letters, but the emotional weight isn't just about choice—it's about the space and time we gave it, which feels lost now.
You're assuming that choosing to write a letter today proves emotional weight, but that's just a small group—most people still go for the quick option.