# Why most of the alkanes are Hydrophobic in nature?

Because the $C - H$ (and more so the $C - C$) bonds are relatively non-polar...
Water solubility, or if you like $\text{hydrophilicity}$, depends on the polarity of the bonds in the solute. Water can dissolve strongly polar materials which feature $O H$ bonds. Water can also dissolve some ionic solutes, where polarity has graduated to complete charge separation.
On the other hand, $C - H$ and $C - C$ bonds are very non-polar, i.e. there is no charge separation that might be solvated by a polar solvent (such as water, or short chain alcohols). And thus the alkanes tend to have little solubility in aqueous media.