When the 4000 was released, many more users complained about wasting either MK or PK because they never used it. Really, photographers are the main ones who like to switch (and even then, not all of them). For the majority of users (proofing, CAD, GIS, etc) they're not interested in switching and so the cost of additional inks, heads, design, etc doesn't interest them either.
Whichever way you go, someone will complain :-)