As is the case with many other technological advancements, this move is simply an attempt by an established global institution to hold onto the little power it still has. As cryptocurrency becomes legitimized by more and more people, the average worker and saver are becoming less reliant on the current system of debt slavery — that's the real reason the IMF recommends against providing legal tender status.
As the crypto market continues to prove itself dangerously volatile, governments should be focused not on banning but regulating these digital transactions so that they don't overtake traditional, more stable currencies, which is exactly what the IMF's latest plan seeks to do. As some national economies have already been negatively impacted by the likes of Bitcoin and others, it's time for authorities to promote trust in their own fiat currencies so that citizens don't get hurt by the unregulated global crypto market.