Well sound is also not matter by wave of energy. but it takes time to travel.... actually slower than light.. as it needs to impart the energy to the next molecule to make it propagate the energy further.. (Just like electricity..through a solid conductor, the atom itself need not move as long as the electron transfer is sufficient to cause the electric current to flow.) If the sound intensity is higher than can be propagated by just vibration transfer, the propagating particle causes the other particle to move as well as vibrate.but why is it not instantanous because it is not actually matter so it does not have to overcome friction to move.
Even light if we consider light in just the wave form.. It is not light that travels but the energy propagated by the particle onto the other that causes the light wave to flow(seemingly). And as we all know transfer of energy takes time (however little it may be) and hence speed. And oreover slow and fast is only relative..to something else. At the moment.. light is relatively faster than all other forms of transfers that we can observe. Our perception of light being slow or fast is limited by our reference of speed. Because one travelling does not care how fast or slow he/she/it is going.. but only try to go at their energy peak.