It's interesting how the rational actions of a bunch of individuals seems to have led to a silly ritual. No one wants to be the jerk who doesn't express sympath

It's interesting how the rational actions of a bunch of individuals seems to have led to a silly ritual. No one wants to be the jerk who doesn't express sympathy for their ill coworker, and they want to fit in as well. So, becoming just one more in the chorus spamming "take care" makes sense.