As others have said. Power limitations and the fact that games development takes time.
If you are expecting something like say... big profile titles like Red dead 2 to be on the switch, it's never happening due to power constraints. But, those Japanese releases that are on the more modest side, like say DQXI. That stuff can com out on the Switch.
But, don't expect high profile third party support. At best some exclusive developed with Nintendo, like the rabbid and mario game.
At the end of the day, it is still a typical Nintendo system. It will not be on par with the "HD" twins. It's just it's quirky thing.