Because long term if we invest in domestic ability to support, debug and improve software is a benefit. Getting actual control over the software deployed, rather then just what Microsoft want's you to get.
Switzerland is behind in Digitization, and having an increase amount of open software to interact and build with makes a hell of a lot of sense. A you do digitization, every part of the software from every deparment needs to interact with every other software. Having this stuff be open source based on open standards, supported by local developers who can make this happen is vital.
We should not just hand our IT infrastructure to Microsoft and Oracle, just as we are not handing of our railway system to Virgin (looking at you Britain).
Of course if its just about LibreOffice, there is no point, we need a much more systematic, wide-reaching long term digitization plan, and open source must be a big part of that.
I frankly don't care if short term it costs a bit more,
Indeed. It's an investment in developing local capabilities.
But they don't just want to do that. I'm not an economist, but I don't think RoI ("return on investment") means the same thing for a government that it does for a corporation. Any money "thrown away" comes back in some way, which creates many opportunities to kill two birds with one stone.