There are 2 reasons:
1. the underpowered hardware
2. the legacy of the Wii: the devaluation of the platform and it's game because of the too many casual shit that were release on the then underpowered Wii, and the milking of Nintendo franchises, thus the dilution of game value in an ocean of sub-standard games, which then had an impact on the Wii U and for now the Switch since it's still underpowered.
This might changes depending on Switch sales growth, but given that the hardware is too far from current PS4/Xbox One/PC settings, developing for the Switch means either making a greatly downgraded version OR making games specifically for the Switch, which means you have to be able to sell a lot on that platform.
This works for light performance indie-games or 5 year old games like Skyrim, but not AAAs or perf intensive indie games.







