Truth is, we are steadily losing many of the former attractions that brought us to diesels - they still shine in economy (to a decent degree), and power. But ever increasing EPA and related environmental regs just keep chipping away at diesel "pluses" - diesels are steadily moving away from their low RPM operation and becoming more like gassers - and the gasser engines keep getting better and closing the gap!
My daughter's '93 Acura 4-banger has 300,000 miles of pretty hard driving on it - never had the heads off, and still runs great - and there are MANY similar gas engines out there proving ya don't necessarily hafta drive a diesel for engine longevity! And don't forget the former price advantage of diesel fuel has pretty much evaporated too...
Then there's the issue of readily available replacement components - Ford, GM and DC gasser parts can be had reasonably easily in more offbeat locations - as well as techs to work on them - certainly NOT true on the diesels! Other than oil changes - relatively cheap themselves compared to a diesel - newer gas engines have greatly extended maintenance schedules.
It may take a few more years, but if current trends continue, the question as to "why a diesel" may become a VERY valid one in other than heavy-duty commercial uses! I seriously doubt I would again buy a diesel if it wasn't for my towing use...