people supporting want a Fat binary that's only fat enough for your particular system, but claim that having fat binaries would solve distribution problems because there wouldn't need to be multiple copies.
these two conflict, if you are going to support FAT binaries for every possible combination of options the distribution problem is much larger. If you are going to want the fat binary to support every possible system in a single binary it's going to be substantially larger.
it's not that I am so opposed to the idea of fat binaries as it is I don't see them as being that useful/desirable. the problems they are trying to address seem to be solvable by other means pretty easily, and there is not much more than hand waving over the cost.