I’m not Christian, but in my life, I’ve known many who have and continue to get tattoos & piercings. So ‘all Christians’ is a broad brush and 2000 years, do you know for sure EVERYONE has rejected it?
Maybe it’s following the New Testament and reading the Old Testament in context. Maybe it’s just different understandings of the text.
Personally, I don’t think God minds tats and piercings one bit.
Here is an article from a Zambian web site warning of the spiritual dangers of tattoos/piercing. It is not Christian.
http://www.frontline.org.za/articles/bodypiercing.htm