a lot of products do NOT contain milk by-products (caseinate, whey, etc) in their ingredients -- and this is one of them -- however, they are manufactured by companies that produce other products that DO have caseinate or whey in them. this is why, after the "ingredients" list, you will often see a warning saying "may contain [milk, wheat, nuts, etc]", or "manufactured on equipment that processes [milk, wheat, nuts. etc]". i believe this warning is required for people with allergies to any of those things.
personally, if casein or whey (or milk) is not listed in the ingredients, then i will buy the product: i am looking for products that do not DEPEND upon dairy for their existence -- i am not looking for a religious standard. one could argue that if you are buying a product manufactured by a company that also manufactures milk products, then you are endorsing the company. that is a very high standard, and would be a very difficult one to follow.
in an imperfect world, we all have to set our own limits.
i would just like to add: boycotting a company because they are "evil" or have horrendous business practices is a different political issue, and certainly worthy of investigation and discretion. however, i am simply addressing the "vegan" issue.