the free market requires manufacturers to keep releasing new products and renew the old ones constantly, or else it would seem old and less attractive to the idiot costumer.
what most companies do in this case is to take the old product, add some new ingrediant to it, renew the logo (or add a "new" stamp) and presto: a whole new product.
in order to add that new ingrediant, the company must get a permit from the FDA (food and drug administration). and in order to get that permit they need to test the ingrediant somehow. now there
are hundreds of tests that does not include animals, but the ones that does include animals are much cheaper to conduct. after all a monkey goes for about 0, a rat for less then 1 dollar.
the companies could choose not to add an ingrediand that requires animals testing, or they could choose and alternative for the test it self but no, they just want more money, they need more money.