Personally I dont think they need it.
Sony tried their hands on MP with a few of their games last gen and wasn't booming so Sony probably knows MP isn't their strengths.
They know many big 3rd party games have a strong hold on the MP market and has it good so why would Sony want to waste time and resources while those 3rd party games help sell their system? It's better for Sony to just market games like CoD and Destiny.
Also I see a lot of people playing Fortnite on PS4 which is completely free so how/why should Sony compete with that lol