Why do houses have shingles and slanted roofs, but most other buildings have flat tops?

Question

Why do houses have shingles and slanted roofs, but most other buildings have flat tops?

In: 8443

Answer 1

Rain moves down off the slanted roof to prevent pooling and leaks, a larger roof is difficult/expensive to build with a slant so may have a generally flattish roof with a slight slope with drainage system removing water from the middle of the roof.