Because a majority of United States citizens have some form of religious affiliation, every person that lives or visits this country (including non-religious citizens) are surrounded by religous references, some more direct than others.
On every US dollar and coin is the phrase "In God We Trust" and every politition ends thier speeches with "...and God bless America."
Over 16% of the United States population is non-religious, meaning that over 50 million people are subject to these things every day.
In the name of religious tolerance and cultral freedom, these unnecessary religius references must stop.