My watercooled system is my main...and most of the time...only system. I take my setup to lan parties and often move the computer into the living room where a larger TV is and use it as a HTPC. So its a must that everything must fit into a case...otherwise, it'll be worthless paper weight.
My first setup I could have all the drives I wanted...as long as it didn't exceed the space of a Mini-Mid Tower
If someone wanted to put a lot of drives into their system, i'm sure they would've bought a server style case.
Also, I can't stand...and can't have external anything...my room is in a constant mess and i'm a clumsy person so external is just asking for a burnt CPU or a large water spill.