This was mostly because they weren't long enough. Doubling them up would have been acceptable. They're more comfortable than many so called InterCity trains, e.g. 221s. There was also an element of the door positions, though I don't agree with this.
Have you ever been on a 175? Bar the luggage racks being a bit small, they have the most comfortable interior of anything I can think of, low density and a mix of airline and table with good window alignment, and very comfortable seats. They're definitely InterCity. The 180, which is unarguably InterCity, has exactly the same interior.
The only annoying thing is them not being walk-through, but then neither is a pair of Voyagers.
If you don't need 125mph, then a pair of 3-car 175s is better in more or less every way, other than the lack of First Class, than a pair of 4-car Voyagers. And First Class is really a bit moot on these services, and hasn't always been there, but it wouldn't be impossible to fit it if ScotRail considered it essential.