Because I get tired of dealing with people who act entitled and refuse to accept simple facts that clearly show a horde bias to the map and even after it has been demonstrated to them countless times and all there falacious and false claims have been shown to be complete and utter nonsense they continue to spout nonsense and admit that the map is broken.
Some simple facts you refuse to accept:
IBGY closes GY is Horde cave which rez’s people at twice the rate of the nearest Ally GY which is 2x farthter away, so even if Ally softcap it the Horde lose nothing.
IBGY is at a very strong choke point that makes if difficult for Alliance to get any significant numbers south without controlling it. effectively making it impossible for Alliance to push to win without capping the GY if the horde are defending. while offering no flank for the Offense to use, instead it has a flank for the defenders to use to bypass an assaulting force or attack the backline.
SHGY once capped by the horde also has a strong northern choke, and has a large flank that allows a team to capitalize on the alliance pushing slightly forward.
If the Horde cap SHGY without the alliance controlling another southern GY they can effectively stop alliance from being able to respawn and can never lose a GY that would let them send waves of horde at any alliance south overwhelming them with numbers. The horde have no such weakness anywhere on the map.
Since the horde have a simple and basic strategy that essentially has no counter to control the map south of SH, they get free access to wolves and Lok to push north with and eventually break any stalemates.
Horde towers are in better locations to provide support to horde defensive locations than the alliance bunkers are.
the list goes on, but like I said its pretty easy for anyone to see that the map gives horde a VERY clear and VERY strong advantage.