Perhaps the title might have been better with a question mark after it? I took it as a theory, please discuss, rather than a statement.
Any grouping of musicians whether a duo, trio or more, works best if they all look and listen and are sympathetic to what each is doing and, yes, well rehearsed, so that they know what's coming.
There are some songs that I prefer to do solo simply because I will vary the tempo, not necessarily the same each time (so how is a duo partner going to follow this?)
However,there is no place for calling people ignorant, Desi C.