I didn't intend to claim that it is because of secularism. I agree with Karl below that it is "history marching progress-ward". I only point it out as a counter-argument to the fear that becoming less religious portends something terrible for mankind. Human progress gives me hope that we can be better. History tells me we can't do much worse.
By "us" I mean humanity. I think most people, regardless of their religious belief or lack thereof, are capable of moral reasoning (There are usually physiological explanations for those who aren't). You attribute it to something supernatural, and I do not.