3 reasons.First, it's your opportunity to highlight any accomplishments you did. Your supervisor knows you and knows what you do, but they don't see EVERYTHING. Your support form is your opportunity to highlight those accomplishments. Chances are your supervisor will at least glance it over or talk to you and your support form helps you in identifying key metrics to bring up.Secondly, a support form is your opportunity to write your own evaluation. Some (a lot) of military supervisors are lazy when it comes to paperwork. Sending them a support form allows them the opportunity to copy and paste it directly to create your evaluation. (*Note, not saying this is a good practice, but, it happens) This gives you the opportunity to highlight just how awesome you area (and sneak in fun phrases to make it onto your evaluation).Lastly, you were told to do your support form. It's a requirement of NCOERs/OERs (which is why evaluations have a spot asking if a support form was received). Ethically, to check that box and not have received a support form would mean your supervisor lied. If it's not checked, and submitted, it will either get rejected by HRC or will make you look like a dirtbag who wasn't doing their job on an evaluation that is in your permanent military record, this can reflect poorly when you look towards promotion boards.Just do it. If you want to do a poor job of it because no one will read it, then that's your prerogative (but not recommended). But at least you can say you did it.