Typical western-world people thinking that they are the only culture on earth...
SE has to take all markets into account. To the proponents of the idea, it may be a nifty addition, but to the opponents, it could be a deal-breaker and jeopardize future sales of the entire franchise.
IMO, the safest thing to do is if they just didn't put a marriage system in at all (let's face it, MMO marriages are equal parts cute, creepy, and meaningless).