SuperTuxKart had gift packages several times in the past.
By offering a FOSS game, we offer a superior service to users, by allowing them to modify, redistribute, etc. STK doesn't contain DRM, it doesn't track its users, it can be freely modded. Most the content is available free of charge.
On the other hand free software developers are also human who need to eat, put a roof over their head, etc. They need to take care of their family.
If you want FOSS projects to succeed, you should want their creators to make more money than they would if they spent their time working on proprietary software, not the opposite.
Making extra content available earlier for donators to help make continued development more sustainable ends up benefiting everyone, because in the end it means more content created overall that will trickle down to the free base game.
