I agree that I wouldn't join in, but can maybe understand why others do.
I had chicken pox as an adult and it was horrible. I was on sick leave from work over 6 weeks. Had an emergency room visit, was on pain pills all day long and sleeping pills at night. On my FACE ALONE I had 90 some odd pox.
I also had them internally and my body was completely covered. I have many many scars all over from them.
I'd truly not wish them on anybody.