Do you remember the days when there were soap bars in the hotel bathrooms? The days when you began washing the hands and then realizing that the soap bar had to be unwrapped? The room service would restock soap, clean the soap dish, and empty the waste basket. Now enter the age of appliances. Many hotels have switched over to "appliances", wall-mounted soap dispensers. They allow for savings for the hotels due to less effort (service, restocking, ...) and are "greener", i.e., the dispensers cause significantly less waste.
The same transition is also happening for database servers. Instead of purchasing hardware (server, storage, network equipments, etc.) and software separately and assemble and test them on-site in a lengthly process, appliances often are delivered ready-to-use (see IBM PureData System). The key to success is to have the right ingredients. Would you use a soap dispenser that says "good for hands, hair, and dishes"? You would expect to have cream soap, shampoo and conditioner, and other cleaning liquids in separate appliances. The same is true for database appliances. That is the reason why IBM (other than some competition ("supports both OLTP and OLAP" )) is offering PureData System for Transactions, PureData System for Operational Analytics, and PureData System for Analytics. Different workloads and requirements need database appliances with different ingredients.
BTW: I still like a nicely shaped, slightly scented bar of soap. It makes the right gift...