Kind of a Berlin problem i guess. In the places i lived before i had UnityMedia and was generally pretty happy with it. In west Berlin you have Kabel-Deutschland which is also okay (but offers only Fair Use Flats yuck), but in the east where i live there is only Telecolumbus if you choose cable. While they offer 400Mbps there are a lot of dense places where people complain about <10Mbps in the evening or the weekends.

In general using Cable, more people have to share the same bandwidth, especially if the provider cheaped out and only does whats necessary. You don't even get your own IPv4, you are basically sharing public IPs with other people through NAT, which makes accessing anything at your home more complicated as well.