Why do electronics components have maximum voltage and not just maximum current?
You most probably don't have a LED 'with a maximum voltage of 2V when powered from a 5GV source', but a LED that is rated for a maximum of 20 mA. 

Components that have a low resistance, and particularly ones that approximately drop the same voltage over a wide current range, are rated for a maximum current, not a maximum voltage.

For most components, voltage and current have a fixed relation that can be found in their datasheet. In most cases it is their product (power P = V * I) through power dissipation that causes a temperature rise above what the integrated circuit material is rated and causes it to fail. The maximum could be expressed in either power or voltage. But when component and temperature variations can cause the same voltage to cause widely different currents, it makes more sense to express the maximum as a current. OTOH, if above a certain voltage breakdown will occur, but the breakdown current is not easy to specify, it makes more sense to express the maximum as a voltage.

Summary: the maximum is generally expressed in the unit that is (for the components at hand) most stable.