Older lenses comes with a more 'collectable' hard case. Like the 80-200, 17-35 or AF 300 f/4 (not the AFS). They are very impractical, but good collectable items IMO.
Newer ones now come with 'soft cases' which is also impractical, and much less value as collectable items.
My 18-70 came in separate lens box, it did have a soft pouch, but I've lost it already.
Many lenses I bought didnt come with any case at all. Even of a $1k+ lens, no pouch/case at all.. Uhh, I'd like it to have a hard leather case, but I dont really care as all my lens cases are here to store some other smaller household items...
I agree with Gary, a good bag will be many times better than idependent lens case!
I know the Sigma lens cases are very cool, they are zipper locked and provides some room for small household items, but can be carried on-field like a belt accessory on the bag.