It is likely because there is a significantly greater number of Horde active in War Mode at the moment. Essentially your shard is the "leftover Horde" shard.
The system maintains a number of shards which attempt to maintain a degree of faction balance within them. When we have an excess of one faction, those are put into their own shard until more of the other faction arises.
Not ideal, and we're doing what we can to reduce the frequency of that occurrence.
https://us.battle.net/forums/en/wow/topic/20766366541#post-2
So theere is an issue with Warmode in wich the factions are very badly balanced overall with some servergroups simply being dominated by 1 faction to an extreme, and that gets reflected in terms of WarMode participation.
Basically, due to the way people have been going to the Horde due to the idea that the Horde is better for PvP, and the devs not acknowledging that enough, they have created a huge inbalance between the factions, and that is causing a lack of Alliance players, and so a lot of shards are consisting of mostly Horde players.
And this will only get worse since the players on the dominating faction can turn on WarMode and get its bonus rewards relative safe, while the oposite is true for the other faction, wich do get attacked a lot, but the rewards are then worthless. And so those players will feel forced to either turn WarMode off, or join the dominating faction, exceterbating the whole issue.
And this whole thing can very easely be fixed by this simple idea:
Make the WarMode incentive bonusses scale to reflect factionsize balance.
Basically the idea is that when the Horde has 50% more players, the Alliance gets a 50% higher WarMode bonus (so 15% instead of 10%)
And it might also work to add a "Call to Arms" type bag (like the one for using the LFG-tool as a needed role) for playing with WarMode on for a certain amount of time wich scales with faction balance; being shorter when there are fewer players on your faction.
And lastly it is a good idea to show faction balance in a UI element together with an indicator that shows how much the WarMode bonus gets scaled.
In the end, there needs to be an honest balance between the risk vs the reward of WarMode. And at the moment, that simply is not there.