The idea that console games being played in multiplayer uses a lot of server resources is false. They do the matchmaking, typically on servers paid for not by Sony/Microsoft/Nintendo but by the game developers, but once clients have been matched together, nearly all games use a peer-to-peer system, meaning that one of the players is the host and their console and internet connection is responsible for all the computational time, electricity usage, and bandwidth usage (which more and more often CAPPED in the US!) The cost of running this is fractional compared to the online store, which handles credit card transactions and the download of game files themselves. Of course, they'd be crazy to charge you just to go into the store. Could they support this service without charging you? Yes. PC games do it, including titles like EA's Battlefront series which do have official dedicated servers rather than peer-to-peer connections. Steam's operating costs are paid for entirely by the cut Valve takes off of game sales (30%, which I think is similar to what Microsoft or Sony take on sales of games for their console.) Other facets of the services, such as VOIP, have ad-driven or even ad-free competitors on every device with a free market (PC, Phone/tablet...)
There's absolutely no way they need to charge that to run the service, it's just a way to scrape more money off of console buyers, and hide the real price of the console. More to the point, the company's costs don't matter. Even if it were for some reason incredibly expensive for companies to run their online networks, and they were generously taking a loss on it after you paid your $60 a year, you'd be foolish to think that's a better deal for you than the free PC ecosystem which exists to this day and shows absolutely no sign of slowing down.
Of course, unless you're really into multiplayer for Mario Kart or Smash, you might feel fine with just not getting Nintendo's premium online service- with the exception of Splatoon, people play Nintendo games for great singleplayer experiences more than multiplayer ones.