Not the one to pigeon hole and instrument... I listened to a couple more of the utube videos.. the harp doesn't seem to fit well in some of the more up tempo / swing jazz tunes..
Being somewhat of a hack on both instruments, in my opinion the biggest reason would be sustain. There's just not enough sustain on the harp. Even on really nice old instruments.
But then again, had Bud Isaacs discovered the harp instead of the steel guitar, we might be arguing from the other side.
