Except it did not work in FFXI. Not when other jobs that happened to be cursed with MP bars were shoehorned into healing because there weren't enough White Mages around. And if they had an advantageous mechanic because they weren't designed to be healers, WHM was then kicked to the curb. We've seen the results already, which makes it surprising to see people that don't want to move on from that type of design.
Yes, console FFs have a staple healer in WHM, and that's fine for console FFs. XI and XIV are MMORPGs, and as such the rules have to be bent and other types of design should at the least be considered, because not everything from the console FFs can effectively translate into an MMORPG.
Depends on the person. As a whole, yes, you have more people that want to DPS over healing and tanking. Now consider how much smaller that number gets when healing and tanking get funneled into 1 class each.Not as many people are interested in playing a HP restorative role as much as "beat them up" or some other role. Thus no need for adding another specific HP restorative role. Especially when you have jobs that support the WHM such as Paladin, Summoner, Bard, Dancer, etc.
As I said in the OP, I hate healing. I've always hated healing. And yet even I found a style of healing I liked to play when I discovered attack heals.