Unfortunately it’s not that easy. Nintendo for example makes many games that use features that are exclusive to their console and porting them over to other consoles would make them so so much worse. Not all games are portable to anything.
I’m not saying it should be illegal to release games for only one console. Obviously not every studio is going to have the bandwidth to develop for every platform, and some games will use special features of some systems.
What I’m saying is that it should be illegal for console makers to give any special incentives or preference to developers to do so artificially.