Managing enterprise software subscriptions – Need for procurement management

One of the biggest shifts in enterprise IT software has been mode of enterprise software purchase. There is a decisive shift towards buying these software through subscription. Though this shift has happened over a period of time – over 10 years or so – but the procurement process has not kept pace with it in most enterprises. 
As a result of which, what challenges are being faced? How it is creating challenges even for compliance and what kind of new approach is needed? 
I am sharing some thoughts here for your consideration.