It's also EXTREMELY useful in jazz comping to know more than 1 (actually you should know a few) way to play a chord.

There are many reasons for this:

1) Exactly what Noticingthemistake said...

2) Sometimes on a real fast song, you may be playing chords around the 9th fret, and only know a voicing for the next chord in open position, or first, and realize you can't make the switch that fast

3)You may want certain chords to have different bass notes, but realize you can't do that by only uing that same chord, unless you want to shorten it, so you can move it down to a different inversion and put the fifth on the bottom..

4)Just getting psyched that you have more options!!!

Hope that helps