Not really Gimp's decision, it is how the GtkFileChooser widget is implemented. One thing you an do:
1) locate a GtKfileChooser.ini on your system (likely somewhere in your C:\users\your_id\AppData on Windows)
2) Edit the line StartupMode to read StartupMode=cwd (the other option is recent)
This will add a line with the current directory near the top of the bookmarks panel in the widget, you can then edit your Gimp shortcuts to start it in some specific directory.
Otherwise you can always add directories in the bookmark panel. The Recently used bookmark is also fairly useful.
1) locate a GtKfileChooser.ini on your system (likely somewhere in your C:\users\your_id\AppData on Windows)
2) Edit the line StartupMode to read StartupMode=cwd (the other option is recent)
This will add a line with the current directory near the top of the bookmarks panel in the widget, you can then edit your Gimp shortcuts to start it in some specific directory.
Otherwise you can always add directories in the bookmark panel. The Recently used bookmark is also fairly useful.