Why have some historians reject the labels bc and ad as labels for periods in world history

Well, if you didn't know B. C stands for Before Christ which is using mainly by Christians and A. D stands for Anno Diomini or the Year of the Lord which again, is used by Christians. They prefer to use B. C. E (Before Common Era) and CE (Common Era) as it doesn't show anything to do with religion. This is what I think.