There is no sense in buying patents jointly with Microsoft because then they couldn't use the patents to block Microsoft from extorting handset makers which defeats the whole purpose. It's not about buying patents for the sake of having patents.
If any of the reporters had bothered to ask an IP lawyer all this would have been made clear to them, but they unthinkingly quote Tweets and print comments from Florian Muller instead.
And are you actually suggesting that producing IP is more efficient and quicker than buying it?! I very much urge you to think on that.