They stated that the reason for the omission was because a much more ambitious multiplayer offering was in the works. Now that it seems unlikely Factions will ever see the light of day, it makes the sting of not having a "normal" multiplayer experience in TLoU2 all the worse.
"Hey buddy, we know you wanted fries with your burger, but if you wait 30 minutes we'll give you a much more delicious side of chicken nuggets"
*30 minutes later*
"Sorry pal, seems the chicken nuggets are not coming after all. Hope the burger was alright"
Me: "Can I have my fries then?"