While not something you should grind for I could see why someone would if they've got the cash.

To give a smaller scale example, when patch hit I wanted to augment my scholar coat, because I love everything about that coat except the color scheme. But it'd cost me about a fifth of my gil. So there's a stingy part of me that says not to do it. But cash unspent, at least in a game, doesn't mean a thing. It's just a number on your screen. So, got my coat, really like it and that money was made back in a week.

Someone min maxing their relic, same thing. A 1 dps upgrade is 1 more than gil normally can buy you. If that gives them some satisfaction, good for them.

Gil's not that useful. So in the rare case you see a chance to buy something you want with it, you should take it.