Here’s one of the problems. Unless one medium can COMPLETELY replace another, there’s little cost reduction, and in fact there’s a tendency for costs to actually go up to convert, and continue both. It’s the same concept as adding channels — social media — without them replacing existing high cost contact points.
There’s lots of exceptions, of course, and government has made some huge strides in paper reduction and convenience by making forms available and even fillable online (pdf).
The real payoff comes down the line if and when the paper steps can be completely skipped.
Think also about digital vs. analog tv. It’s a good example of how transitions are challenging, and don’t immediately produce cost savings if you have to run two different “methods”.