Why did the US conduct a Census of Religious Bodies, and why did it stop?

[dqa]

The US conducted a Census of Religious Bodies from 1906 through 1936. Even prior to that, there were apparently questions about religion on the regular decennial census .

in 1850, the census included inquiries on social issues, such as taxation, churches, pauperism and crime.

The Bureau itself is not very helpful:

The Bureau of the Census collected information in the Census of Religious Bodies from 1906-1936. This information was obtained from religious organizations.

Public Law 94-521 prohibits us from asking a question on religious affiliation on a mandatory basis; therefore, the Bureau of the Census is not the source for information on religion.

[ol]
[li]Was the decision by the newly formed (1903) Bureau of the Census to measure religious organizations in 1906 simply a continuation of previous practices, or was it a new policy?[/li][li]What happened in 1936 or afterward which caused the Census Bureau to discontinue this practice?[/li][/ol]