Melanotan (melanin injections) as treatment for Vitilago (read description)

Recently i stumbled across this comment about vitilago that really got me thinking. Basically the comment made was "why do people with the condition choose to lighten their whole body, instead of make the lighter patches darker?" Now let me be clear. I am not trying to debate the condition at all.

My question is, is there a lack of resources one with the condition can obtain to darken their skin tone? Or is this just a reflection of colorism (as the comment implies)?

I looked up a couple treatments and i found this article attached to this study for Melanotan (melanin injections) and some kind of UVB treatment actually having successful results.

However, melanotan is not FDA approved and is illegal currently in the UK.