Hey Herr_Reitz, it's not uncommon for games of a same company to do cross promotional offerings or targeted promotions (you'll see us doing them with World of Tanks from time to time). This is part of our every day marketing efforts across multiple platforms. The idea behind this isn't for you to abandon PC to play mobile, but if you are a mobile game player (and many of us are) why not enjoy Ships in a different way?
The offer is certainly not for everyone, but giving away a few items is usually required to push people over the edge of installing and trying it out.