It's because people generally tend to expect, and in many ways demand, conformity. There's an idea about what a console traditionally should be, and Nintendo simply does not cater to those expectations. They pretty much consistently strive to make something different and unique every time, and as much as people like to act as if they want unique things, it's usually not true. People want tried and true. Tried and true controls, features, hardware design, etc...the more consistent the better.
Nintendo is "wacky." One year their console is a cube that plays little baby disks, then suddenly the next console abandons normal controllers and you're waving a stick around your room nonstop, then they throw that out and put a tablet with thumbsticks in your hand, now maybe we're gonna go "backwards" a good decade or so and bring back cartridges.
Compare that to the very straightforward evolution of Sony and MS consoles, and it's easy to see why Nintendo is viewed so differently. Sony and MS play things safe for the most part. Nintendo takes a lot of risks, and that simply doesn't always pan out







