I believe it's also a holdover from medieval times.
The kings seldom taxed over 10% ... because if 10% was good enough for god, who were they to ask for more?
(too bad government doesn't think that way, any more. LOL)
I've also pointed out in the past, that if churches were using all that money for "good works" they wouldn't have multi-million-dollar buildings. How many people could have been helped by the funds that went into building the Crystal Cathedral, for instance?
I mean, they are spending 6 years and $2million to renovate the organ.
btw - one of my favorite songs is Ray Stevens' "Would Jesus Wear a Rolex".