It is because historically, ingredients for use in cosmetics had to be tested on animals for safety reasons, this was the way things were done. Nowadays, new ingredients cannot be tested on animals unless for certain safety reasons, if there is no other alternative. Alternative ways of testing new ingredients are generally more expensive, so there is a lack of innovation in the area for new ingredients, unless you have people willing to pay through the roof for your product. Therefore most manufacturers continue to use ingredients that were historically tested on animals. This is even for popular companies making cruelty free claims; there are always loopholes, but I won't go into that.

Of course I also dislike animal testing, though I am more desensitised after reading for 3 years at university about how many ferrets etc were sacrificed to see how for example, influenza works (obviously I know cosmetic testing is not necessary compared to disease/drug studies). But I get annoyed at companies that use the cruelty free claim to try and sell more product when really, some of their ingredients may have had historical animal testing.