What is the reason that vpn is prohibited on some sites?

E.g. Netflix or Crunchyroll it doesn't make a difference yes they have different series in each country but why is it illegal to use vpn? It makes no difference whether I watch vpn in Germany or fly to America and watch the series there

It's not banned, Netflix just blocks it. Netflix wants you to be able to watch local programming at the local price. It also has something to do with the rights for the films / series.

The Netflix subscriptions cost differently everywhere. The licenses are issued for individual countries. DoS attacks are made more difficult by a VPN blockade.

Edit: Here is an example. I opened Netflix with a VPN server in Turkey. Converted to cost 11 euro less per month.

They only have licenses for certain countries and the authors want the VPNs to be blocked.

This is prohibited for them because you can no longer effectively restrict geo-restricted licensing to the licensed area if the customers circumvent this via VPN.
Only companies should please benefit from globalization.

Maybe not in the two countries. But imagine you are in a "traditional" country, where you can expect reprisals if it comes out that you have seen two men "look deep into each other" in a series. Netflix & Co. Then have to adjust their offer accordingly for these countries, i.e. Not make content available. If you then use VPN, however, your "origin" is concealed and you could access content that is undesirable in this country. And that's why - because the providers don't want to get dirty - VPN is "forbidden" on some sites. And oh yes: there may be different prices for the bookable packages in different countries - and we don't want the user to illegally generate an advantage somewhere ;-)

But it doesn't have the same offer as in Germany or the USA.

Hoster and VPN protocol?

What discounts do you have to make and do you get original sound with German subtitles?