@mcc that's the thing tho - if you dig down you can keep answering "why" to a point, but then... Why SU(3)xSU(2)xU(1)?
At some point, are the fundamental symmetries that give rise to the standard model feel arbitrary; the values of the masses of the particles, the strength of the fundamental forces, and the coupling constants feel arbitrary; this is (in part) why we still have string theorists.