Why does it make more sense for the hydrophilic sugar-phosphates to be on the outside of the dna molecule and the hydrophobic nitrogenous bases on the inside? what other cellular structure do you know of that has a similar orientation?

The answer is in the question if you think about the meaning...but here is my input.

Since the lipids/sugar phosphates are hydrophilic, it would want to stay away from water. The opposite is for the hydrophobic nitrogenous bases. This way, the components of the DNA molecule won't be soluble in water, which the cell is mostly made out of. This similar structure can be found in a vesicle or cell-membrane.