Actually, between those DX re-releases and SNES to GBA ports, Nintendo's been doing "remasters" for quite a long time now that I think about it. I wonder if they know quite what the sell through is on them.
Those GBA games for example make me imagine they're massively sold to people who already own the original. Like I imagine the people who wanted to play LTTP, SMB3, etc. on the go are not the kids propping up the DBZ, Yu-Gi-Oh, etc. games that dominated the other part of the sales charts back then. Then again, I think Minish Cap is one of the worst selling Zelda's so the audience for that on the GBA just might have been small overall.
edit:
Oracle of Seasons + Oracle of Ages: 3.96 million
LTTP GBA: 1.81 million
Minish Cap: 1.76 million
Phantom Hourglass: 4.76 million
interesting, this tells me absolutely nothing about my theories
