Is there any reason for "saving" variables?

I've got this function a colleague once has written:

setSentence: function (e) {
  this.setState({
    issueText: e.target.value
  });

  if (this.refs.messages.textContent.length > 0 && e.target.value.length > 2) {
    this.refs.messages.textContent = '';
  }
},

He uses e.target.value on two places within the code. I would tend to make something like this:

let textBoxContent = e.target.value;

Then use the variable with the more descriptive name instead.

I once talked to him about these avoiding variables-thing. He just said that he wants "to save variables".

Would like to change these code-pieces but I'm still not sure ...

So therefore my question:

Does "saving variables" respectively avoiding variables in the code make any sense?