Ellyn
Veteran
Why label yourself?
Uh...so that people will know, recognize, and perhaps even honor the aspect of your lifestyle reflected in the label as part of regular social communication?
"Come over for Christmas, we have a honey-baked ham!"
"I don't eat ham, I'm vegetarian."
If the label went, "I don't eat ham, I'm Muslim" then the one doing the inviting would know to switch to roast beef instead of tofu turkey. If the self-labeling went "I don't eat ham, I'm pescetarian" then it might take some more explaining because that's not a popularly-known term, but the result would be that the one doing the inviting would know that switching to halibut is an option.
It's not a frivolous label. It's a way to communicate adjustments in behavior that we all make in society. It's not like, "I can't eat gluten, I'm Goth" which makes no sense. Or, "I don't eat nuts, I'm agnostic" -- that's when I'd wonder, "Why label yourself like this? Gluten has nothing to do with shopping at Hot Topic or listening to Marilyn Manson."