Because they give up their First Amendment rights in order to get kickbacks from the Federal Government and their members can get tax deductions on their donations...

As a result of the COVID-19 outbreak, the Treasury Department and the Small Business Administration have loosened restrictions on many of their lending and grant programs to include participation by churches and non-profit organizations.

For the purposes of these programs, churches are considered 501(c)(3) organizations and are directed to claim this designation on their SBA application, as long as they meet the following requirements:

• the organization must be organized and operated exclusively for religious, educational, scientific or other charitable purposes;

• net earnings may not inure to the benefit of any private individual or shareholder;

• no substantial part of its activity may be attempting to influence legislation;

• the organization may not intervene in political campaigns; and

• the organization’s purposes and activities may not be illegal or violate fundamental public policy.

Note that the entities administering these programs – including the Small Business Administration and lending institutions across the country – are currently facing a significant influx of applications.

https://sewell.house.gov/sites/sewell.house.gov/files/COVID%20Fact%20Sheet%20for%20Churches.pdf

If you truly want to know. I highly recommend reading this: https://www.creationliberty.com/articles/501c3.php

Wrong....

Churches never had to pay taxes. The only reason many register as 501(c)3 organizations is so their members can claim tax deductions on their tithes, not realizing they are giving up control of their churches to the government.

There's a lot of carrot/stick behavior going on to get churches onboard and register as 501(c)3 organizations, which is why the majority of churches have indeed registered as such.

Remember when the Indianapolis Baptist Temple was seized by the IRS during the Bush administration because they didn't play ball and decided to preach the Gospel in spite of the warnings? Of course you don't.

Feds seize Baptist church over $6 million tax debt

*By Associated Press Feb 13, 2001, 1:56pm MST *

"I can say personally, this has been as difficult a task as I've had in my 37 years of law enforcement," said U.S. Marshal Frank Anderson, who read the order urging those inside to leave. "We waited 91 days for the safest and most opportune moment to act; we didn't want anyone from our side or the other side to get hurt."

https://www.deseret.com/2001/2/13/19569270/feds-seize-baptist-church-over-6-million-tax-debt

There's occult significance to why the IRS chose to wait until February 13 to seize the property.

Also, 91 days is also exactly 13 weeks...

Now what happened to one of the members of that church after the IRS took away their 501(c)3 status? They were ordered to pay back taxes on their contributions that had legally been deducted in prior years.

https://www.courtlistener.com/opinion/4555355/taylor-v-commissioner/