Hetzner has some weird and very strong opinions on what you can and cannot do on their servers, likely because they are so cheap they attract all sorts of shady customers.
It's quite a bit broader than that [1], and so worth being aware of as it's stricter than many US providers, but unless you happen to fall in one of those categories it's also not a big problem:
"This includes in particular, but is not limited to, pornographic or obscene material, extremist content or content that offends common decency, gambling, material that could seriously endanger the morals of children or young people or violate the rights of third parties (copyrights, name rights, trademark rights and data protection rights). This also includes the publication of defamatory content, insults or disparagement of persons or groups of persons."
On top of that there's a blanket ban on crypto.
Personally I've used them for 15+ years at a number of companies and never had a problem. But I accept some people will want to set up content that violates or skirts close enough to break those rules to be uncomfortable.
Another way of saying that is, "they don't want spammers as customers since that can negatively effect other (good) customers".
Which I'm just fine with.