Ha! I get what you're saying...but were those houses painted in bog standard colours @50kHobbyJob (eg, white, magnolia, timeless etc)? Or something a bit more 'interesting'?
I agree that many houses are painted, say, white throughout (walls, ceilings, doors, all other joinery) and think in the past we've bought a few like that, although we've always bought project houses that have needed immediate, complete renovation. So, in our particular case, as part of the bigger project, we've stripped wallpaper/re-skimmed if necessary, then painted in (usually deep) colours of our choice - however, prior to early 2018, this was not normally the same colour everywhere in a room.
I first became aware of the idea of what is now referred to as 'colour drenching' when visiting some NT properties and also specifically in 2017 when I fell in love with the interiors of one of the houses in BBC's Taboo, which I proceeded to replicate when we moved house early in 2018. Initially we painted walls, ceilings and joinery of our hallway in F&B Drawing Room Blue, which - when we reconfigured the upstairs landing - we changed to F&B Inchyra Blue. It was so successful, we went on to adopt the style in various other rooms and are now doing the same in our new-to-us cottage.