I don't know about you...but I have several devices that accept CF or SD media...like my laptop, my PDA, my already existing card reader, ect. So do a lot of other people out there, like my family and friends. If I bought a sony camera, that only used sony memory sticks, then I'd have to have a sony reader of sorts at each of these places that I'd like to view my pictures at.
There are many times when I'll yank out my media card, toss it in carrier, and then haul it either to work or over to a friends house to look at the pics. Same goes for viewing while out and about. I can yank the card out of my camera and toss it into my PDA for storage.
No can do with memory sticks. Got to have a special reader to use them.
Bleh.