I disfavor wasting recording time or effort on a purely instrumental offering.
The Richard Carpenter Trio began life as an instrumental group, and Richard Carpenter was the driving force behind that. Richard is a gifted piano player and his talents deserved his own small space on a Carpenters album.
Remember, in 1970, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, and 82, no-one, NO-ONE, had even the slightest thought that there would be limited time with Karen on Earth. The future would always be full of many more vocal tracks with Karen shining through. Under those circumstances, didn't brother Richard deserve even a little space?