Why?
(I'm on the fence in this myself)
Well, ignoring the principles of the thing for a second, this will absolutely set off riots and create further division in Germany. It'll be a fun few days for news crews and police forces there.
But coming back to the principles of the thing, it's scary to create what is essentially now a two-tiered society in Germany, especially along lines that concern peoples' private medical information. If someone has made the choice not to get the vaccine, they should have the right to make that choice without their freedoms being limited, especially when 70% of Germany's adult population are already vaccinated. If someone doesn't want to get vaccinated, I'll be disappointed with them, but (especially in western and central Europe) there are enough people jabbed now that we can pick up the slack for those who didn't want to. Vaccine efforts should be about striving for a common good -- the majority doing their part so that
everyone can carry on as normal.
And who's to say that it'll stop at those who are unvaccinated? What if there's people in Germany currently saying "Well, I've had two jabs and I'm willing to take my chances with COVID now, so I won't have the booster". Will non-boostered people be locked out of public life until they've been injected a third or fourth time, like a good, obedient citizen? This is a government wielding far too much power over its citizenry, and it's doing so by guilt and in the name of "protecting public health". Last year, things like lockdowns were probably necessary and so, in a bit of a panic, we opted for them. But I remember being told almost a year ago that "we won't get back to normal until the vulnerable are vaccinated". A year on and we're still being told "you'll only get X when you do Y" or "if you don't do X then Y will happen".
So yeah, bonkers and scary move from Germany's government.