My Dad died recently and although he was an atheist, and always has been, I received a great deal of pressure to agree to a religious service. My brother, who is a believer said, "What's the harm?". I suggested a Muslim cleric and a Jewish rabbi as well as the Lutheran pastor that he had already decided upon. "Well, that's different he said"
"How so?" I responded, "he didn't believe in any of these religions, why not choose all of them?" In the end, I was able to get the pastor to give a secular service, as secular as possible that is. Not what I felt my Dad would have wanted, but he probably wouldnt have gotten too bent out of shape about the service.
People usually dictate the end-of-life care they want to receive, or whether or not they want to be cremated, but seldom express the type of funeral they want and this lack of communication can lead to hard feelings, especially for those who are theists and dont understand why a secular funeral is important for non-theists.