Having played a long neck a long time ago the answer I believe lies in its versatility of keys for a vocalist. If you're tuned in D and want to sing using the same pattern in C you simply slip the capo up the neck two frets and retune the fifth string to F or C. I was playing in a band at the time and we changed keys a lot. Because we specialised in 3 or 4 part vocal harmonies we oftimes had to choose weird keys to fit our vocal ranges. The long neck worked just fine, but I'd agree that it was never ergonomically ideal to play up near the nut for extended periods.
Slight change of subject but I installed a vioiln fine tuner for the fifth string on the bridge plate. For speed on re-tuning on stage it was one of the best tricks I ever had, and complemented the extended neck nicely.