There were various factors working against this album having been a more 'true' singles album like the 1969-1973 album though. In late 1978, they were also releasing Christmas Portrait, so already had something to promote (this wasn't really an issue in the UK, where Christmas albums generally weren't popular and the album accordingly was given next to no promotion). Richard was also at his nadir health-wise, so was in no position to start augmenting and embellishing new arrangements/segues for the album. Plus - and this is the key factor I suspect - by late 1978 in the US, they were completely out of favour on the singles charts. Compilation albums released during an artist's active career tended to only do well if their recent commercial standing was reasonably robust (the 1969-1973 Singles album had been well-served by 'Top of the World' going to #1 around the time of the album's release). By late 1978, the Carpenters hadn't had a Top 30 single since mid-1976 and their last two singles had missed the Top 40. Even if the album had been given that extra attention in terms of arrangements/segues, I suspect it would not have sold well in the US because they were at such a low ebb commercially. In the UK, by contrast, 'Calling Occupants' had made the Top 10 only a year earlier, so they didn't have that same problem to overcome in that market.