There’s a big cultural barrier between the two ends of the cable. Quarter-inch jacks are indestructible, ancient and roadworthy. They were introduced in 1878, for use in telephone exchanges, and they’re still in almost any piece of musical equipment you’d ever want to use, from a Les Paul to a Moog Modular. They never break, and if they do happen to fray, can be mended by anyone who knows which end of a soldering iron to hold. With no tools, a combination of sharp teeth and nimble fingers can make a workable repair.
Meanwhile the new-fangled USB plug, introduced in 1995, has no place in rock’n’roll. It’s invariably plastic, and was literally designed by a committee. Neutrik does produce a nickel-housed USB socket that could almost fit on a guitar amp, but would be unlikely to survive attack from a flying bottle of beer.
In the last year, USB/Guitar hybrids have been everywhere. The GuitarPlug does the same job as the Lightsnake, without the attached cable or the glowing LED. Towards the end of 2005 there was a rash of USB guitars, released by many, bought by few, culminating in the Behringer iAxe, a $149 guitar with a built-in USB socket and a bundle of free software. I’m sure it sounds great.