I blame Adaptec for the dominance of IDE. Seriously.
If Adaptec A) hadn't had the lionshare of the SCSI mindset in the PC business back in the 90s, and B) hadn't made so much overpriced buggy crap, we'd all be using SCSI today.
Yes and No. I remember playing with it back in the 90's and what drove me away from SCSI was the complexity of the standard. Yes Adaptec made it harder then it had to be but IDE, for all it's failings, was easier to use. You jumper'd one disk as master and one as slave and it pretty much just worked. SCSI on the other hand, at least in DOS/Win3/Win95/98, was a complex process involving TSR's and fiddling with jumpers on the disks & HBA. I remember my father spent six hours trying to get a simple SCSI scanner to work.
By the time RedHat 6 came out, when I made my first real foray into Linux, SCSI support was a lot better. I also took the time to sit down with a sysadmin I knew and download his knowledge about SCSI which he'd learned over the decades.