Arghhh!!!
Have they ever heard of a game called Killer Instinct!!!!!?
Didn't KI have to hire the creator of GGPO to optimize it just for that game though? Maybe it was SF though. Either way its not that simple and I'll explain why.
In the cases where major studios had to hire the GGPO creator to work with them to cut down on development hangup on learning to use his code optimally with their engine you run into something. If that guy is currently tied to anyone else's game development he may not have been up for hire to work on this due to non compete clauses or simply due to still being involved in working with them or others on their own products. They would have had to buy in and work on GGPO from scratch themselves and depending upon the engine its not always easy. I'm using Unity for my fighter and it codes in C# which GGPO is STILL not working for. Depending on what coding language their engine utilized it could have been a LOT of money and effort to use someone else's code and if that is the case it may just get broken in the translation process of trying to use it anyway...
Rage a little less is all I am saying. This is the business world we're talking about here. Its not just cut and dry and "it should say GGPO" because its not that simple. Its not a thing you tack on. The game has to be coded for it. Skullgirls was coded from scratch for it with its engine. KI as well. Its a big deal to use code outside of your development team's own code and it comes with a long winded learning curve everytime to optimize it.
GGPO isn't completely plug and play. Its something you have to learn how to develop for. The amount of time and effort needed to do this can hold up entire sections of game development and in the game development world delays on a game are critical and can ruin it. Deadline hell is grueling. Folks have been known to just live at the studios for weeks on end during them because no more money is coming and no more time is allowed...they either release a complete deal thats quality or get burned at the stake by every "angry game reviewer" that exists on forums, youtube and at magazines until their is no selling their product.