Why do you send text messages after donating blood?

Here we will send two (just remember roughly):

1 (2-3 days after blood donation) Dear Mr. XXX, you donated blood on XX, XX and passed the inspection. Thanks for your support.

2 (After blood was sent from the blood bank) Dear Mr. XXX, the blood you donated on XX, XX has been sent to XX Hospital for clinical application. I thank you on behalf of the recipients.

The premise of texting seems to be to agree to join the emergency blood donation when filling out the form.

I hope I can help you.