oh, I meant, is it because there are Amiga drivers only for voodoo cards?
I presume that nowadays there are lot more powerful PCI graphic cards than 3dfx?
It's the driver situation. S3 cards are weak sauce (I dunno, maybe they're OK comparatively for the Amiga), nVidia cards are pretty much closed-source on the drivers, so that leaves Voodoo cards or ATI, and I don't know that there are drivers for classic Amigas for the ATI chips.
So that leaves either the old old
old Zorro cards, or s3, or 3dfx.