Because there are many, many, many Nintendo enthusiast fans. "Hardcore", in short words, and while they may only make up for 100K users (just a guess), this minority is very vocal over the web.
Just a guess, again, because I see that Nintendo fans can compete with Xbox and PlayStation ones in terms of presence; at least in some sites.
My bet with The_Liquid_Laser: I think the Switch won't surpass the PS2 as the best selling system of all time. If it does, I'll play a game of a list that The_Liquid_Laser will provide, I will have to play it for 50 hours or complete it, whatever comes first.