Firstly, because there are hardly any public IPv4 addresses still available and we are not one of the tech giants of the last century who have secured address blocks on an opulent scale. As a colocation operator, we of course have a few IPv4 addresses, but not to the extent that it would scale with our business goals in the long term.
Secondly, we are friends of promising technologies and like to work on the edge! Green power and decentralization are an integral part of our concept. The modern IPv6 protocol is a perfect fit for this. And without compromise: Internally, we rely on IPv6-only, which allows us to reduce complexity compared to combined IPv4/IPv6 environments and to pass on the resulting price advantage to you as a customer. IPv4 is only available in the form of NAT64/DNS64 services, which connect your colocation (invisible for your devices) with the IPv4 world. Details can be found in How is my colocation connected to the internet?