For generic consumers i.e. individual users, not considering data centres:
Why does acoustic levels and power consumption make such a huge difference especially on externally powered drives? I would believe it would make sense to consider these factors for 2.5" laptop / battery driven harddrives.
For such large drives which are possibly on a desk - who cares what power it draws (possibly significantly less than a light bulb?) and what noise if makes since it would be sitting on a desk!
Apart from the cost factor, the more power it draws the more heat it creates, not what you want in an external enclsure.
As to the noise factor, while you may be willing to put up with it, most are not.
Personally noise isn't an issue even though I have 5 hard drives in my workstation. Heat however is very important and can kill a hard drive over time. External enclosures are horrible for daily uses as they slow and allow drives to get hot. Plus they are problems in the making when concerning most users who at least once drops the enclosure while a drive is installed. Worse while the drive is powered up and in use. In the end its better to keep them inside the machine or outside as a bare drive.