Why does SO2 and water make H2SO3 and NOT H2SO4?

SO₂ is a polar molecule and dissolves in water to form H₂SO₃; however, it does not have the ability to break the H-O bond in water and isolate an Oxygen atom to form H₂SO₄. This is why in the production of Sulfuric acid via the contact process, SO₂ is converted into SO₃ first.

SO2+H2O = H2SO3

To get H2SO4,

SO2 must be oxidized to form SO3, Sulfur tri-oxide

2SO2 + O2 = 2SO3 SO3 can the dissolve in water to form acid rain:

SO3 + H2O = H2SO4