Why did Nintendo stop with all the periphels? Iask this because if you look at sales numbers, their best years are when they release them. Their best years I'd say were 07-09.

In 2007 was the first year ever for the the actual wii mote, and they released the Wii Zapper

In 2008: this year the introduced more new add ons. They released the Wii Wheel, Wii Fit, and wii Speak

In 2009: This year they showed off Wii Fit Plus and Wii Motion Plus which both became an instant hit.

In 2010 and 2011 however, nothing. Absolutley nothing. And I think it's one of the factors that hurt their sales in the last 2 years. They didn't introduce anything really new to the audience anymore. ANd it's probably why microsofts sales rised randomly in the last 2 years, because they introduced Kinect. I don't think the the 360's sales would be where they are now if it wasn't for kinect.

So why do you think Nintendo felt the need to stop using these add ons when they were selling?

It's because people were catching on. Consumers figured out that things like the Zapper, Wii Wheel, Nunchuck, and Balance Board were just useless add ons. They didn't want to push it with that Vitality Sensor thingy.

First off the Wii Mote was released in 2006 the same year the Wii launched. So I assume you must be talking about the Wii Mote being sold with a lesser game Wii Play in 2007. The Wii Zapper I was also sold with what was essentially a "demo game" in the same fashion with the Link Crossbow game. I think Nintendo threw them in to add value to games that really wouldn't have been worth the cost if sold on their own. As far as the Wii Wheel it was also originally also packed in with Mario Kart, but I am sure that was more a way to spur additional wii wheel purchases because I know it worked with me buying a second wheel the day it came out. I don't think the Motion Plus was able to pull off additional purchases the same way despite being included with a few games. I've never seen official sales figures on the Wii Speak but I don't know of anyone that actually bought it and that would explain its quick disappearance.
The "most successful" years of the Wii that you mention is more of Nintendo was able to catch lightning in a bottle twice. First with Motion Play and Wii Sports and a steady release schedule of AAA games in the beginning and then just when there was a hint of Wii supply catching up with demand Wii Fit was released and brought along a lot of casuals who were originally on the fence and every soccer mom that was duped into thinking it was real fitness product.