The effect of the EM field upon a charge $q$ is given by the [relativistic Lorentz](https://en.wikipedia.org/wiki/Lorentz_force#Relativistic_form_of_the_Lorentz_force) force equation:

$$\frac{dP}{d\tau}= qF^{\alpha\beta}U\_{\beta}$$

The expression on the RHS is then substituted via Maxwell's equations to define EM field conservation laws and their corresponding definitions of field energy and momentum within them. Is there a physical reason for defining the energy and momentum of the electromagnetic field this way?