And that's why I'll return you to my post about push. If there is no backing behind a peripheral, it becomes an accessory, not an upgrade or an expansion. Expansions work only if they're properly integrated, like for example Brood War, which almost all Starcraft players joined because it was just right.
Also, the point you make on cash-ins may give an answer to the unexpected and possibly bloated success of the Wii, just sayin'. It all boils back to causality. If an accessory has no appeal, then it is not worthy of being a full cycle-enducing piece of tech, let alone warrant a new console.
I'm not sure if you see my point, but it's there.
Brood War is a game, not a hardware expansion on an existing console. Big difference.
The Wii Fit board is the most popular hardware expansion of all time and look at all the support that got. No hardware expansions will ever come close to a new console release.
Switch Code: SW-7377-9189-3397 -- Nintendo Network ID: theRepublic -- Steam ID: theRepublic
Switch - Super Mario Maker 2 (2019)
Switch - The Legend of Zelda: Link's Awakening (2019)
Switch - Bastion (2011/2018)
Switch - Mario Kart 8 Deluxe (2014/2017)
3DS - Star Fox 64 3D (2011)
Wii U - Darksiders: Warmastered Edition (2010/2017)
Mobile - The Simpson's Tapped Out and Yugioh Duel Links