Depends on how it is calculated, if it is after tax that isn't so much.
Also, people who are supporting church will often use a lot of their services so it's not like giving money to a charity you will never directly see their work (like environmental groups).
Finally, the 10% rule comes from times where the state had a much lesser role in fighting poverty.
Exactly. At most churches, tithes mostly pay for the physical plant and the full-time staff (who provide services in the form of weekly lectures, counseling, misc. community organizing, and sometimes directly contribute to physical plant upkeep as well).
Tithing is more like a PBS membership or seomthing.
Also, people who are supporting church will often use a lot of their services so it's not like giving money to a charity you will never directly see their work (like environmental groups).
Finally, the 10% rule comes from times where the state had a much lesser role in fighting poverty.