It seems odd that they insist on putting the power connectors on the top of the card instead of the back which would avoid a lot of space constraint issues.
It also indicates there might be a market for a specialized 90° connector that can squeeze into tight spaces like that.
I'm not sure I agree here; a lot of consumer cases that I've worked with are just barely deep enough to house a card of this size. Putting the power connector on the end of the card would add some extra room to make the case slimmer perhaps, but most consumer cases tend to be generously wide, while not having a lot of extra depth. Wires plugging into the end of the card would compete with the hard drive / CD ROM / Media Card Bay, etc etc.
I agree with nVidia's choice here, but you also raise a valid point; certain cases and configurations would benefit from the added flexibility of that adapter, so there may well be a market.
I had an Antec case (solo or sonata or something like that) where I had to cut into the drive bays with tin snips to fit a 1080ti. Modern cases have more room for GPUs.
Power on the top of the card makes it easier to fit in most cases. When it's on the end of the card, you usually have to connect the power before installing the card. You also get a much nicer cable bend on top since the cables don't have to twist.
Consumer cases tend to be fairly wide, to accommodate 5½" drive bays and tall CPU coolers. Length tends to be the primary constraint on GPU size in these applications.
It also indicates there might be a market for a specialized 90° connector that can squeeze into tight spaces like that.