Because without third parties they don't have enough software to use. Unless they have nothing but indies, but even then their selection is sparse compared to other consoles, and I don't think it would tempt many people to pay up

I will probably quit console gaming altogether if Nintendo started charging for online play and they'd make more money selling games than giving them out for free.

I think it would be smart to try. $9.99/month. Give away games like PS Plus. Something on both Wii U and 3DS, maybe a VC game and something from this gen each month. No one uses their online for gaming much... That's the truth... So you can't really use playing online as an incentive to pay. Maybe do some sweet giveaway each month. Few random people win Nintendo shirts or collector pins.

Honestly Nintendo would lose money in that situation. The bulk of the games Nintendo sells are their own games. They'd be giving away what they are already selling.

I don't think giving away games a year old or so in a subscription-service is a good idea for Nintendo. I don't think it is a good idea for Sony. I have only to look how it changes my behaviour towards Playstation. I decided I don't need to buy any game, just wait what I get via PS+. Also I don't buy a PS4 or Vita yet. If I buy them some years down the line I'll have a lot of games to play. So Sony loses a lot. Otherwise I would buy games I'm interested in and the purchase of a new system would have higher priority.

But a premium subscription service could work for Nintendo. There could be free giveaways of Virtual Console games. That Nintendo is willing to give them away for free was shown at the launch of the WiiU, where you could get one monthly VC-game for a symbolic price. Also give sales for subcription-owners for limited times or drop the price a bit more for subscribers in the sales already happening. So most people get off 20% for a month, subscribers 30% for example. Also nintendo has already a premium-subscription service - PokeBank. That could be integrated in a Nintendo-service. Take 10 €/$ for a year and that could work.

They can keep online play free, but a new "Club Nintendo" premium subscription service  is necessary for their future business. 

The thing with teh subscription services is that I do not WANT or NEED monthly "free" games. It's too much and simply I will be flooded with them and never finish all. There may be some I like but rest would probably be not for me.

Waste of money. However......a subscription services where I pay for all the internet stuff such as using the store or playing online would be good for me.

But I'm not complaining about the perfectly great FREE online I get from Nintendo.

Compared to Sony and Microsoft they don't have a lot of online content as far as games go so that is probably why they have nothing similar to PS Plus and Games with Gold.

ps plus has saved me hundreds of euro on games. how is that a bad thing? you also discover many great games you'd never otherwise have bought. it's a service loved by millions and nintendo doing it would be the best thing ever for those who don't buy all their games upon release. 

their online service is  by far the worst of the big 3. ps3 has free online and it's currently a lot better than the wii u online. i strongly disagree with your description on nintendos online as perfect.