text: Because water is polar.  Polar molecules can create favorable interations (hydrogen bonds) where + and - charges match up, for an energetically favorable configuration.  Lipids (fats and oils) are non-polar, and do not forma favorable interactions with water and other polar solvents.  Hence, they keep to their own--polar and polar go well together, and nonpolar goes with nonpolar.  Hence, hydrophobic (water fearing) and lipophilic (fat loving) mean the same thing.