I agree, it's interesting to see the different reason(ing)s for not celebrating birthdays.
Still, in the context of Christianity I'd consider it "going over the top". As opposed to "celebrating self" you could also focus on "being thankful for your life, family, friends, ...".
I can't really speak for other faiths, of course, but I'm friends with a "cultural Muslim" family in Germany (mom grew up Catholic) and they did celebrate birthdays.
More and more I get the impression that being "fundamentalist" (of whatever religion or conviction) seems to foster the attitude that anything with a chance of "being fun" is either "immoral", "sinful", "unhealthy", "wasteful", or "..." (fill with negative adjective of your choice) and therefore undesirable.
(Sorry for the snarkiness - but only a little.