I mean, can you imagine? Stranger knocks on your door wearing a yellow vest and carrying a blood draw kit...
You: Can I help you?
Stranger: Yes! I'm here to take a blood sample from you!
You: Oh, great! So you're a certified phlebotomist?
Stranger: Uh...sure?
You: Hmmm. Sounds legit to me! Come on in, stranger with a needle and very questionable credentials. I'll put a pot of coffee on!