Because values change over time. I'm not sure if that's what you're asking. Species are not the only things to evolve...cultural ideas evolve also...in this case, values.
Yep - values change, not sure "evolve" is the correct word. "Lower standards", "devolve", those come to mind.
I was just reading about some pre-Revolution churches - most wouldn't allow Tories. Now I wonder if the SBC would have the brass to take a stand like that. More than just a potential loss of revenue for them, back then.