The sales strength and chart time of The Singles 1969-1973 obviated any need on the part of
the record company (or the duo) to have to have an album (any album) in 1974.
Yes, don't discount the impact of SINGLES 1969-1973. It wasn't just a thrown-together greatest hits package. There was arranging to do, parts to be sung, and lots of studio work. "Ticket To Ride" got its total re-do here. The Overture needed to be arranged and recorded, and Karen's parts for the segues needed to be done. While it wasn't a full album's worth of work, it DID take time to accomplish what is now considered one of the best-ever compilation albums.
Harry