Only for certain items
I buy blank DVD's for many 'run from DVD' or 'Live' Linux versions. I also buy them for backup purposes.
I do buy a 'store bought' movie sometimes. Especially when the distributors can only sell them for a very limited time, like with many of the Disney Movies that are only allowed to be broadcast or sold every generation.
Another item is that even Netflix doesn't carry all movies. No site does due to extremely unreasonable copycrap laws.