GUEST, If tunes were made up entirely of arpeggios, there would be only one set of chords for each tune. This isn't the way it is. Most tunes can be accompanied by many different progressions without altering the tune.
James Taylor used a simple, folky 2 chord progression to accompany his instrumental intro and outro for Oh Susannah, but used a much more complicated 2 chords per measure progression for the vocals.

(A)I come from Alabama with a banjo on my (E)knee.

(A)I come from (Am7)Ala(Bm7)bama (F#m7)with a (A)banjo (F#m7)on my (Bm7)knee(E7)

Even for the same song, like Sally Good'n or Tennessee Waltz, you would not use the same chords for a bluegrass version as for a Western swing version.