Thanks Neil. It occurred to me after posting that another good reason is to enable easier vibrato string bending. I'm not advanced enough to do that myself but it seems that it's a lot easier to bend strings in the middle of the fretboard than down closer to the nut.

I often see songs in tablature using fairly straightforward chords in the first 1-4 fret positions, but if there's a solo melody within the song, the tablature then uses higher fret positions, such as frets 5 to 10. All of those same notes can also be found in frets 1-5, so I wonder why it's necessa...