1. People who don't believe in God couldn't give a rip whether we religious believers are inconvienenced in our religious practice.
2. We are asking our fellow citizens to give up something they value, without offering anything they value in its place.
3. We sound like we are whining about ourselves. No one finds whining appealing.
You can read about these reasons in further detail, and the strategy of argumentation Roeback offers in place of religious liberty, here.
Stand firm in Christ,