Gydion: Yes, I've see it before. Not sure how much I consider a button to be a UI though... GOG uses Wineskin for all their Wine wrapped OS X games. Which is an extra bonus to be familiar with it.
Even just a single button can be a surprisingly effective way to lower the barrier of entry for many, many users, especially users who aren't comfortable with using the command line to configure WINE, or like I, would rather opt to use a dialog with buttons vs. the command line.
Gydion: Well, kind of my point. I don't particularly see why an OS X user wouldn't be able to use just Wine. I agree Wineskin is more accessible, but installing the WineHQ packages is exceedingly trivial. Using it isn't particularly difficult either. First time it would be a good idea to take a few minutes and read up on it.
Different strokes for different folks. The vast majority of OS X users aren't used to using Terminal to run their apps, even though tools like MacPorts and Homebrew/Cask have made it a lot more easier and a lot more accessible. People -- OS X users in particular -- just want an easy (somewhat) to follow graphical UI with graphical elements like buttons and dialogs to access WINE, and/or a file they can double-click and run, which is why tools like Wineskin and CrossOver are so popular on the Mac. Using the command line may be trivial and completely intuitive for some people, but that doesn't mean that it's trivial and completely intuitive for all. :)
In any case, I thought it fair to assume the OP wanted a fast and easy way to install their game using WINE with a minimum of effort and time required. If he/she wanted to use the .pkgs via Terminal, there's plenty of information out there on Google to help them do it.
For bug reports, they could easily report what environment they used WINE in, and others could weigh the usefulness of their reports accordingly, just like what they do now with people who post reports using different versions of WINE on different OSs or on different hardware.