Thats how they made it, so yes, its normal. :]
And as for this being one of those Game Freak questions, It pretty much is... but its Okay.
Also, Like Dt said in his comment,
Most HM's are meant to help you outside of battle,
By doing things like Cutting Down Trees, Smashing Rocks, and Sailing across Water.
So it's very normal that most HM's are Water Normal and Fighting type.