[murligenius (OP)]

why cant elctromagnetic waves transfer energy in a straight line.......

[Soul Surfer]

They do!  You are confusing the changes in electrical and magnetic field intensities represented graphically by changes in physical position like a fly following a zig zag track.

That was the flippant answer here is the deeper one.

Electromagnetic waves transfer energy from place to place without the clear physical structure of a particle which can be moved from one place to another  to do this it is necessary to have two different energy storage mechanisms  in this case it is charge in the form of an electric field and current in the form of a magnetic field locally the charge and the current are oscillating together and energy is flowing in the process. it is probably easier to think of in terms of other wave motions that we can see and understand more easily.  Water waves on the surface of the sea transfer energy along the surface of the see by transferring energy between the potential energy of the height of the wave and the kinetic energy of the movement of water.  The wave itself moves along in a particular direction but the water molecules do not flow with it all they do is move up and down and backwards and forwards in small circles or ellipses.