[prostoalex]

The reasons are mainly historical, but the non-profit lobby (consisting of charities, 501c3 non-profit organizations, churches and university endowments) holds so much power, that stripping them of tax-sheltered status would be a third rail for any politician running for office.

The historical reasons assume that many everyday community efforts (feeding the hungry, sheltering the homeless, abused women and children, planting trees, sheltering stray animals) is better done (and financed) at community level by community efforts rather than by central government and sending money to Washington D.C.