The main reason I use hide glue is because I believe the bond to be better, it gives more wood to wood contact and it uses less glue overall than any other adhesive. Hide glue dries hard and crystalline and most likely causes the vibrations in the guitar to be transmitted in a more efficient way.
Using rope is the traditional way of attaching the binding to the guitar while the glue dries. All the Spanish makers used and continue to use it. I have strong convictions about this and believe it is an important element of making the best sounding guitars.