I don't agree that aesthetic features have little purpose in a desktop application - they are a major part of the user experience. In this case the transparency feature is clearly something that a lot of people consider worth having.

Everything in life is not about productivity. But even if it was, the aesthetics of your environment does impact productivity. Personally I do continuously tweak the appearance of my environment because being relaxed and at ease makes a big difference to my concentration, which makes a big difference for how easily I get in the zone and is productive.

To presume that a feature that is "just for aesthetic reasons" has little purpose is arrogant and/or implies a lacking understanding of other developers.