The Soviets made this a favorite way of forming the names of policies and organizations, like Comintern from Communist International, and agitprop , from agitation and propaganda . The resolutely anti-communist Time Magazine was no less creative, coining words like cinemogul . The process picked up more steam after the war, and it's been at full throttle in recent years. The entertainment people have given us cineplex , blaxploitation , infotainment , dramedy , and rockumentary . Politicians have given us Medicare and Reganomics .
Businesspeople talk about permatemps , infopreneurs , coopetition .
In the past few generations, English has introduced more portmanteau words than in all the previous centuries back going back to Chaucer. There are naming consultants who have programs that can grind out endless lists of these things. In the words of the old punchline, because they can. This helps to explain why portmanteau words are usually so transparent. In this sense they're the opposite of slang, which percolates into the language from cliques and in-groups, and which is usually designed to be opaque to people who aren't in the know.