Is it really necessary to clear a variable before overwriting it?

Hello Experts,

I might be asking a dumb question but I havent really found an answer for this anywhere.

Is it really necessary to do this:

CLEAR l_material.

l_material = 'ARandomMaterial'.

I have seen the above snippet in several programs and even well experienced ABAPers write it.

Is the approach to consider a variable as a Slate or a Black board is correct  or is it just a mere waste of human effort in reading and writing the code?