To make a third party game across all consoles, you have to develop it for all consoles, which takes resources, which means your estimated revenue needs to overcome those expenses, for starters. But then you have to factor in possibilities of those developers working on something new and getting a better ROI with their time working on that.
For example:
If Team A makes Game A and releases it on console A, selling 6 million copies, and they project if they sold it on console B it would sell 2 million copies, but if they don't it would speed up development on their next game releasing on Console A by a year or two, which itself will sell another 6 million copies, then it may not be financially worth it to even bother with Console B.
If they have money to throw at a porting studio they could, but then that's once again money that could be invested in more *new* game development that has a better ROI. They could, instead of paying a porting studio money to port a game already made, invest that money in expanding their internal studios so they can push out more new games quicker.







