I'd have to disagree. Don't get me wrong now, guitar is awesome, but to say that with just an accordion and fiddle something is missing?
I have a house dance at my place in the fall and spring and trust me, just an accordion and fiddle gets em dancing just as much as any other combo, or all three.
I definitely know what you're saying though! If I was recording a front porch, minimalist kind of cd, It would for sure have guitar.
But let me just add my 2 cents. As someone who plays both accordion and rhythm guitar in cajun music. The rhythm guitar is and should be a "thankless" position. Its not even remotely near the level of difficulty as it is to play accordion or fiddle which requires persistent practice to learn and improve upon. Not to mention the chord progressions in cajun music are very simple and basic. Rarely does the music move outside of the 1,4,5 chords and there are tons of great songs which use only two chords the entire time.
In the context of cajun music, quality rhythm guitar playing can be learned in a matter of months, while quality accordion and fiddle playing takes years.
No doubt there are better gigs for a good picker, but it's still an important component of the music.
With a little imagination, the job can be made more interesting. Case in point: Jon Bertrand's quirky stage presence certainly adds to the persona of the Pine Leaf Boys.