Yes, it well and truly sucks.
Anyway, I think one of the possible major reasons they kept GBA compatibility at all is to make memory cards. Seriously, a gigabit isn't going to hold all those large, large RPGs companies love so much, which used CDs that hold a heckuva lot more than 128 megs. Since FtM has proven the DS can read GBA games while running DS games, it makes sense that these multi-card games could have access to saves on a seperate GBA cart while they go on their merry way, therefore eliminating any problems carrying saves from one cart over to another. (Of course, if the cart is in on its own or in a GBA/GBP, then you get the traditional menu that lets you organize your saves.)
Of course, while I think this is a GREAT idea (I mean, who doesn't want RPGs of FFVII and PDS calibur on a Nintendo portable?), I know Nintendo's not going to go for it, causing companies to opt for the PSP and all its shortcomings in favor of having space to do things.
EDIT: Figures that Mystic says the same kind of idea while I'm posting. :P