It seems to me that highest note depends on where we started. Not all songs start on the tonic, of course. I think the composer gets started,then composes a tune which goes about an octave - often an octave plus one note. Then they wind up on the tonic.

The excludes pentatonic tunes, naturally.

There is a Catholic song book called Breaking Bread which has tunes from any eras in it, from Gregorian to yesterday. I've just glanced about about 30 songs in it, and each one ended on the tonic.