Ah, choice. Additional components, additional complexity, additional cost. Once committed to this double-feature, how does a company abandon choice without stirring a hornets nest of dissent? What criteria will Apple use to determine when "consumer choice" becomes "the consumer has spoken?" Like Abraham bargaining for the survival of Sodom and Gomorrah, would 30% usage be enough to continue offering a particular choice? 20%? 10%?
In this particular context, "choice" is just another way of saying, "I don't want to change. Change is OK for the other guy, but not me."
Yeah, Touch ID has been a very successful feature. It may seem counter-intuitive to abandon a successful feature for a new one, but that's generally the way things go.
I once owned a house that was built to support both gas lighting and electric. Effectively a matter of, "We don't know if this new-fangled electric stuff is going to work out." There was gas piping running under floorboards, above ceilings, and inside walls, all to support a "choice" that was never used. In the end, all it did was complicate renovations. Even more ironic, the house originally had a coal furnace/water heater, and coal kitchen stove. Those were replaced by gas. Alas, no wood-burning fireplace, and the oil industry never got a foothold.