Unfortunately, the product-buyers at the major retailers aren't toy enthusiasts, so don't have an interest in what they sell, and will just focus on whatever the toy-distributors promote to them. Greater profit comes from doing the least amount of work (for the major chains), so they'd be happy for the toy-distributors to do as much work for them as possible (store displays, promotions, discounted stock, etc).
That's why toy-distributors would do something catchy like a "top 10", for the product-buyers to remember more easily, over competitors' products. Keeping the line-up small and simple, caters to the major-chain retailers who see one toy product as being the same as another (a mere product to profit from).
The toy-distributors will still continue to push their other products while they have a foot in the door, but the bulk of their product sales (volume) will be of those 10 lines, compared to anything else they have at the moment.
As for the Furbys - Hasbro & Mattel resurrect old toylines after a break, as they are new to a new generation (which is only about 3-5 years in toy years). They've updated the electronics to give them more features, but the Brand/concept, like Ponys, Strawberry Shortcake, Voltron, MOTU, Cabbage Patch Kids, etc, will keep coming back every few years.