Licensing your idea to an established company has many advantages. Your product will carry the label of a company that has a well known and respected name. Most individuals cannot, and should not approach large companies like Wal-Mart, Target, etc. They usually will not look at people who only sell one product, they prefer vendors with multiple products. Most larger companies have a complete marketing and Public Relations department.
Larger corporations have the capital and resources available to launch a product properly.
By allowing another company to build and market your product they generally assume the liability also. Thus if for some reason something happens that has legal ramification they will usually handle it. You get paid royalties for doing nothing. Of course it is your idea, you did invent it and file the appropriate patent application. But what we mean is that you will get paid, while they build it, market it, promote it, and do all of the ground work.