Which makes the tax declaration much more complicated. Additionally this can easily cause lots of trouble with the employment contract.
I mean sure, since I am a libertarian, I prefer there to be no hurdles and no taxes at all, but the majority of people think different. And you are not even a libertarian I suppose? So you just want a excemption from taxes/buerocracy for you? Or just for small things like donation? Yeah well, this is the case right now, but they need to somehow verify that it is indeed small. I found the current situation reasonable. A bit more effort with tax declaration, but not really much, having a small business.
"Additionally this can easily cause lots of trouble with the employment contract."
And this is a problem with your contract then, which you negotiated and nothing for which the state is responsible.
I am not against taxes per se, but I am a deep hater of bureacracy.
Unless of course, you say you are non profit - then they have to accept that, complicated, yes.
But if you want small donation money for a webpage, it is very easy. You register a small company for it (cost 20-30€, time 20 minutes at the finance agency. and you can use that company for many other similar things). And then you are legally good to receive money in all forms, bitcoins or not. They don't care how you got that money. All that matters to them is how much profit you made in a year. If it is below 16000€ you don't pay (company) taxes - and they totally ignore you for being not important. If you make higher income, well, then you start having a serious business, with taxation and probably more regulation, true.
But for small things I found it not so hard.