It's a pretty outdated design considering that not many games ever had Rumble Pak support and I don't believe there were any other GBA-format accessories. The current DS hardware iterations don't even have GBA slots anymore!
The existence of the GBA cart pegs in the DS case does provide a nice alternative for GBA owners who want to house their games in something sturdier than their original cardboard boxes.
Yep for GBA games.. I find it pretty useful as I store my GBA games in related DS game cases to make them easier to find, i.e. Zelda Minish Cap goes in the Spirit Tracks case, etc.
[quote name='rapsodist']The existence of the GBA cart pegs in the DS case does provide a nice alternative for GBA owners who want to house their games in something sturdier than their original cardboard boxes.[/QUOTE]
www.thecoverproject.net has just about every GBA game cover custom-made for a DS case for exactly this reason. And it looks fantastic to those with the will to purchase tons of blank DS cases and print out all of the needed custom covers.