Why do I have Honor Points even though I have never done PvP?

Whenever your faction holds the Wintergrasp world battleground, all members of your faction gain the buff 'Essence of Wintergrasp' while in Northrend.

During Wrath of the Lich King, the Essence of Wintergrasp buff would allow the collection of Stone Keeper's Shards by performing certain actions - including the completion of Wrath of the Lich King dungeon instances.

In Cataclysm, Stone Keeper's Shards were converted into honor points, with the new honor/conquest system that was implemented. As a result of this change, any future instances where you would have previously gained Stone Keeper's Shards now result in you collecting a small quantity of honor points, which will most likely be how you got yours without doing any PvP.

There are a number of quests in Grizzly Hills that provide Honor Points as a reward. You may have done some of those while levelling.

Having Wintergrasp gives you honor instead of the tokens that where removed when killing bosses in instance.

A fast search I found this:

You had wintergrasp for the second boss, the stone keeper shards you would have gotten pre-patch are instantly converted to honor points for lack of a better explanation.

source

I recently solo'd normal Violet Hold on my level 85 mage. I was awarded 2 Honor Points for the end boss. I got these instead of ye olde Stone Keeper Shards.

http://us.battle.net/wow/en/game/patch-notes/4-0-1

All Arena Points, Honor Points, Battleground Marks of Honor, Stone Keeper’s Shards, Venture Coins, and Spirit Shards have been converted into new Honor Points.

Honor Points will be awarded instead of these currencies, with the exception of Arena Points.